diff --git a/packages/SystemUI/src/com/android/systemui/util/concurrency/MessageRouter.java b/packages/SystemUI/src/com/android/systemui/util/concurrency/MessageRouter.java
new file mode 100644
index 0000000000000..542cf6559c64d
--- /dev/null
+++ b/packages/SystemUI/src/com/android/systemui/util/concurrency/MessageRouter.java
@@ -0,0 +1,198 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.systemui.util.concurrency;
+
+/**
+ * Allows triggering methods based on a passed in id or message, generally on another thread.
+ *
+ * Messages sent on to this router must be processed in order. That is to say, if three
+ * messages are sent with no delay, they must be processed in the order they were sent. Moreover,
+ * if messages are sent with various delays, they must be processed in order of their delay.
+ *
+ *  Messages can be passed by either a simple integer or an instance of a class. Unique integers are
+ *  considered unique messages. Unique message classes (not instances) are considered unique
+ *  messages. You can use message classes to pass extra data for processing to subscribers.
+ *
+ *  <pre>
+ *      // Three messages with three unique integer messages.
+ *      // They can be subscribed to independently.
+ *      router.sendMessage(0);
+ *      router.sendMessage(1);
+ *      router.sendMessage(2);
+ *
+ *      // Three messages with two unique message classes.
+ *      // The first and third messages will be delivered to the same subscribers.
+ *      router.sendMessage(new Foo(0));
+ *      router.sendMessage(new Bar(1));
+ *      router.sendMessage(new Foo(2));
+ *  </pre>
+ *
+ * The number of unique ids and message types used should be relatively constrained. Construct
+ * a custom message-class and put unique, per-message data inside of it.
+ */
+public interface MessageRouter {
+    /**
+     * Alerts any listeners subscribed to the passed in id.
+     *
+     * The number of unique ids used should be relatively constrained - used to identify the type
+     * of message being sent. If unique information needs to be passed with each call, use
+     * {@link #sendMessage(Object)}.
+     *
+     * @param id An identifier for the message
+     */
+    default void sendMessage(int id) {
+        sendMessageDelayed(id, 0);
+    }
+
+    /**
+     * Alerts any listeners subscribed to the passed in message.
+     *
+     * The number of message types used should be relatively constrained. If no unique information
+     * needs to be passed in, you can simply use {@link #sendMessage(int)}} which takes an integer
+     * instead of a unique class type.
+     *
+     * The class of the passed in object will be used to router the message.
+     *
+     * @param data A message containing extra data for processing.
+     */
+    default void sendMessage(Object data) {
+        sendMessageDelayed(data, 0);
+    }
+
+    /**
+     * Alerts any listeners subscribed to the passed in id in the future.
+     *
+     * The number of unique ids used should be relatively constrained - used to identify the type
+     * of message being sent. If unique information needs to be passed with each call, use
+     * {@link #sendMessageDelayed(Object, long)}.
+     *
+     * @param id An identifier for the message
+     * @param delayMs Number of milliseconds to wait before alerting.
+     */
+    void sendMessageDelayed(int id, long delayMs);
+
+
+    /**
+     * Alerts any listeners subscribed to the passed in message in the future.
+     *
+     * The number of message types used should be relatively constrained. If no unique information
+     * needs to be passed in, you can simply use {@link #sendMessageDelayed(int, long)} which takes
+     * an integer instead of a unique class type.
+     *
+     * @param data A message containing extra data for processing.
+     * @param delayMs Number of milliseconds to wait before alerting.
+     */
+    void sendMessageDelayed(Object data, long delayMs);
+
+    /**
+     * Cancel all unprocessed messages for a given id.
+     *
+     * If a message has multiple listeners and one of those listeners has been alerted, the other
+     * listeners that follow it may also be alerted. This is only guaranteed to cancel messages
+     * that are still queued.
+     *
+     * @param id The message id to cancel.
+     */
+    void cancelMessages(int id);
+
+    /**
+     * Cancel all unprocessed messages for a given message type.
+     *
+     * If a message has multiple listeners and one of those listeners has been alerted, the other
+     * listeners that follow it may also be alerted. This is only guaranteed to cancel messages
+     * that are still queued.
+     *
+     * @param messageType The class of the message to cancel
+     */
+    <T> void cancelMessages(Class<T> messageType);
+
+    /**
+     * Add a listener for a message that does not handle any extra data.
+     *
+     * See also {@link #subscribeTo(Class, DataMessageListener)}.
+     *
+     * @param id The message id to listener for.
+     * @param listener
+     */
+    void subscribeTo(int id, SimpleMessageListener listener);
+
+    /**
+     * Add a listener for a message of a specific type.
+     *
+     * See also {@link #subscribeTo(Class, DataMessageListener)}.
+     *
+     * @param messageType The class of message to listen for.
+     * @param listener
+     */
+    <T> void subscribeTo(Class<T> messageType, DataMessageListener<T> listener);
+
+    /**
+     * Remove a listener for a specific message.
+     *
+     * See also {@link #unsubscribeFrom(Class, DataMessageListener)}
+     *
+     * @param id The message id to stop listening for.
+     * @param listener The listener to remove.
+     */
+    void unsubscribeFrom(int id, SimpleMessageListener listener);
+
+    /**
+     * Remove a listener for a specific message.
+     *
+     * See also {@link #unsubscribeFrom(int, SimpleMessageListener)}.
+     *
+     * @param messageType The class of message to stop listening for.
+     * @param listener The listener to remove.
+     */
+    <T> void unsubscribeFrom(Class<T> messageType, DataMessageListener<T> listener);
+
+    /**
+     * Remove a listener for all messages that it is subscribed to.
+     *
+     * See also {@link #unsubscribeFrom(DataMessageListener)}.
+     *
+     * @param listener The listener to remove.
+     */
+    void unsubscribeFrom(SimpleMessageListener listener);
+
+    /**
+     * Remove a listener for all messages that it is subscribed to.
+     *
+     * See also {@link #unsubscribeFrom(SimpleMessageListener)}.
+     *
+     * @param listener The listener to remove.
+     */
+    <T> void unsubscribeFrom(DataMessageListener<T> listener);
+
+    /**
+     * A Listener interface for when no extra data is expected or desired.
+     */
+    interface SimpleMessageListener {
+        /** */
+        void onMessage(int id);
+    }
+
+    /**
+     * A Listener interface for when extra data is expected or desired.
+     *
+     * @param <T>
+     */
+    interface DataMessageListener<T> {
+        /** */
+        void onMessage(T data);
+    }
+}
diff --git a/packages/SystemUI/src/com/android/systemui/util/concurrency/MessageRouterImpl.java b/packages/SystemUI/src/com/android/systemui/util/concurrency/MessageRouterImpl.java
new file mode 100644
index 0000000000000..7145c775fe399
--- /dev/null
+++ b/packages/SystemUI/src/com/android/systemui/util/concurrency/MessageRouterImpl.java
@@ -0,0 +1,186 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.systemui.util.concurrency;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Implementation of {@link MessageRouter}.
+ */
+public class MessageRouterImpl implements MessageRouter {
+
+    private final DelayableExecutor mDelayableExecutor;
+
+    private final Map<Integer, List<Runnable>> mIdMessageCancelers = new HashMap<>();
+    private final Map<Class<Object>, List<Runnable>> mDataMessageCancelers = new HashMap<>();
+    private final Map<Integer, List<SimpleMessageListener>> mSimpleMessageListenerMap =
+            new HashMap<>();
+    private final Map<Class<?>, List<DataMessageListener<Object>>> mDataMessageListenerMap =
+            new HashMap<>();
+
+    public MessageRouterImpl(DelayableExecutor delayableExecutor) {
+        mDelayableExecutor = delayableExecutor;
+    }
+
+    @Override
+    public void sendMessageDelayed(int id, long delayMs) {
+        addCanceler(id, mDelayableExecutor.executeDelayed(() -> onMessage(id), delayMs));
+    }
+
+    @Override
+    public void sendMessageDelayed(Object data, long delayMs) {
+        addCanceler((Class<Object>) data.getClass(), mDelayableExecutor.executeDelayed(
+                () -> onMessage(data), delayMs));
+    }
+
+    @Override
+    public void cancelMessages(int id) {
+        synchronized (mIdMessageCancelers) {
+            if (mIdMessageCancelers.containsKey(id)) {
+                for (Runnable canceler : mIdMessageCancelers.get(id)) {
+                    canceler.run();
+                }
+                // Remove, don't clear, otherwise this could look like a memory leak as
+                // more and more unique message ids are passed in.
+                mIdMessageCancelers.remove(id);
+            }
+        }
+    }
+
+    @Override
+    public <T> void cancelMessages(Class<T> messageType) {
+        synchronized (mDataMessageCancelers) {
+            if (mDataMessageCancelers.containsKey(messageType)) {
+                for (Runnable canceler : mDataMessageCancelers.get(messageType)) {
+                    canceler.run();
+                }
+                // Remove, don't clear, otherwise this could look like a memory leak as
+                // more and more unique message types are passed in.
+                mDataMessageCancelers.remove(messageType);
+            }
+        }
+    }
+
+    @Override
+    public void subscribeTo(int id, SimpleMessageListener listener) {
+        synchronized (mSimpleMessageListenerMap) {
+            mSimpleMessageListenerMap.putIfAbsent(id, new ArrayList<>());
+            mSimpleMessageListenerMap.get(id).add(listener);
+        }
+    }
+
+    @Override
+    public <T> void subscribeTo(Class<T> messageType, DataMessageListener<T> listener) {
+        synchronized (mDataMessageListenerMap) {
+            mDataMessageListenerMap.putIfAbsent(messageType, new ArrayList<>());
+            mDataMessageListenerMap.get(messageType).add((DataMessageListener<Object>) listener);
+        }
+    }
+
+    @Override
+    public void unsubscribeFrom(int id, SimpleMessageListener listener) {
+        synchronized (mSimpleMessageListenerMap) {
+            if (mSimpleMessageListenerMap.containsKey(id)) {
+                mSimpleMessageListenerMap.get(id).remove(listener);
+            }
+        }
+    }
+
+    @Override
+    public <T> void unsubscribeFrom(Class<T> messageType, DataMessageListener<T> listener) {
+        synchronized (mDataMessageListenerMap) {
+            if (mDataMessageListenerMap.containsKey(messageType)) {
+                mDataMessageListenerMap.get(messageType).remove(listener);
+            }
+        }
+    }
+
+    @Override
+    public void unsubscribeFrom(SimpleMessageListener listener) {
+        synchronized (mSimpleMessageListenerMap) {
+            for (Integer id : mSimpleMessageListenerMap.keySet()) {
+                mSimpleMessageListenerMap.get(id).remove(listener);
+            }
+        }
+    }
+
+    @Override
+    public <T> void unsubscribeFrom(DataMessageListener<T> listener) {
+        synchronized (mDataMessageListenerMap) {
+            for (Class<?> messageType : mDataMessageListenerMap.keySet()) {
+                mDataMessageListenerMap.get(messageType).remove(listener);
+            }
+        }
+    }
+
+    private void addCanceler(int id, Runnable canceler) {
+        synchronized (mIdMessageCancelers) {
+            mIdMessageCancelers.putIfAbsent(id, new ArrayList<>());
+            mIdMessageCancelers.get(id).add(canceler);
+        }
+    }
+
+    private void addCanceler(Class<Object> data, Runnable canceler) {
+        synchronized (mDataMessageCancelers) {
+            mDataMessageCancelers.putIfAbsent(data, new ArrayList<>());
+            mDataMessageCancelers.get(data).add(canceler);
+        }
+    }
+
+    private void onMessage(int id) {
+        synchronized (mSimpleMessageListenerMap) {
+            if (mSimpleMessageListenerMap.containsKey(id)) {
+                for (SimpleMessageListener listener : mSimpleMessageListenerMap.get(id)) {
+                    listener.onMessage(id);
+                }
+            }
+        }
+
+        synchronized (mIdMessageCancelers) {
+            if (mIdMessageCancelers.containsKey(id) && !mIdMessageCancelers.get(id).isEmpty()) {
+                mIdMessageCancelers.get(id).remove(0);
+                if (mIdMessageCancelers.get(id).isEmpty()) {
+                    mIdMessageCancelers.remove(id);
+                }
+            }
+        }
+    }
+
+    private void onMessage(Object data) {
+        synchronized (mDataMessageListenerMap) {
+            if (mDataMessageListenerMap.containsKey(data.getClass())) {
+                for (DataMessageListener<Object> listener : mDataMessageListenerMap.get(
+                        data.getClass())) {
+                    listener.onMessage(data);
+                }
+            }
+        }
+
+        synchronized (mDataMessageCancelers) {
+            if (mDataMessageCancelers.containsKey(data.getClass())
+                    && !mDataMessageCancelers.get(data.getClass()).isEmpty()) {
+                mDataMessageCancelers.get(data.getClass()).remove(0);
+                if (mDataMessageCancelers.get(data.getClass()).isEmpty()) {
+                    mDataMessageCancelers.remove(data.getClass());
+                }
+            }
+        }
+    }
+}
diff --git a/packages/SystemUI/src/com/android/systemui/util/concurrency/SysUIConcurrencyModule.java b/packages/SystemUI/src/com/android/systemui/util/concurrency/SysUIConcurrencyModule.java
index b9b20c73c5d57..e9e794ea884b6 100644
--- a/packages/SystemUI/src/com/android/systemui/util/concurrency/SysUIConcurrencyModule.java
+++ b/packages/SystemUI/src/com/android/systemui/util/concurrency/SysUIConcurrencyModule.java
@@ -170,4 +170,20 @@ public abstract class SysUIConcurrencyModule {
     public static Executor provideUiBackgroundExecutor() {
         return Executors.newSingleThreadExecutor();
     }
+
+    /** */
+    @Provides
+    @Main
+    public static MessageRouter providesMainMessageRouter(
+            @Main DelayableExecutor executor) {
+        return new MessageRouterImpl(executor);
+    }
+
+    /** */
+    @Provides
+    @Background
+    public static MessageRouter providesBackgroundMessageRouter(
+            @Background DelayableExecutor executor) {
+        return new MessageRouterImpl(executor);
+    }
 }
diff --git a/packages/SystemUI/src/com/android/systemui/util/leak/GarbageMonitor.java b/packages/SystemUI/src/com/android/systemui/util/leak/GarbageMonitor.java
index edea3055a783a..c7998882876ac 100644
--- a/packages/SystemUI/src/com/android/systemui/util/leak/GarbageMonitor.java
+++ b/packages/SystemUI/src/com/android/systemui/util/leak/GarbageMonitor.java
@@ -36,7 +36,6 @@ import android.graphics.drawable.Drawable;
 import android.os.Build;
 import android.os.Handler;
 import android.os.Looper;
-import android.os.Message;
 import android.os.Process;
 import android.os.SystemProperties;
 import android.provider.Settings;
@@ -60,6 +59,8 @@ import com.android.systemui.qs.QSHost;
 import com.android.systemui.qs.logging.QSLogger;
 import com.android.systemui.qs.tileimpl.QSIconViewImpl;
 import com.android.systemui.qs.tileimpl.QSTileImpl;
+import com.android.systemui.util.concurrency.DelayableExecutor;
+import com.android.systemui.util.concurrency.MessageRouter;
 
 import java.io.FileDescriptor;
 import java.io.PrintWriter;
@@ -110,18 +111,18 @@ public class GarbageMonitor implements Dumpable {
     private static final int DO_GARBAGE_INSPECTION = 1000;
     private static final int DO_HEAP_TRACK = 3000;
 
-    private static final int GARBAGE_ALLOWANCE = 5;
+    static final int GARBAGE_ALLOWANCE = 5;
 
     private static final String TAG = "GarbageMonitor";
     private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
 
-    private final Handler mHandler;
+    private final MessageRouter mMessageRouter;
     private final TrackedGarbage mTrackedGarbage;
     private final LeakReporter mLeakReporter;
     private final Context mContext;
-    private final ActivityManager mAm;
+    private final DelayableExecutor mDelayableExecutor;
     private MemoryTile mQSTile;
-    private DumpTruck mDumpTruck;
+    private final DumpTruck mDumpTruck;
 
     private final LongSparseArray<ProcessMemInfo> mData = new LongSparseArray<>();
     private final ArrayList<Long> mPids = new ArrayList<>();
@@ -133,13 +134,16 @@ public class GarbageMonitor implements Dumpable {
     @Inject
     public GarbageMonitor(
             Context context,
-            @Background Looper bgLooper,
+            @Background DelayableExecutor delayableExecutor,
+            @Background MessageRouter messageRouter,
             LeakDetector leakDetector,
             LeakReporter leakReporter) {
         mContext = context.getApplicationContext();
-        mAm = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
 
-        mHandler = new BackgroundHeapCheckHandler(bgLooper);
+        mDelayableExecutor = delayableExecutor;
+        mMessageRouter = messageRouter;
+        mMessageRouter.subscribeTo(DO_GARBAGE_INSPECTION, this::doGarbageInspection);
+        mMessageRouter.subscribeTo(DO_HEAP_TRACK, this::doHeapTrack);
 
         mTrackedGarbage = leakDetector.getTrackedGarbage();
         mLeakReporter = leakReporter;
@@ -158,13 +162,13 @@ public class GarbageMonitor implements Dumpable {
             return;
         }
 
-        mHandler.sendEmptyMessage(DO_GARBAGE_INSPECTION);
+        mMessageRouter.sendMessage(DO_GARBAGE_INSPECTION);
     }
 
     public void startHeapTracking() {
         startTrackingProcess(
                 android.os.Process.myPid(), mContext.getPackageName(), System.currentTimeMillis());
-        mHandler.sendEmptyMessage(DO_HEAP_TRACK);
+        mMessageRouter.sendMessage(DO_HEAP_TRACK);
     }
 
     private boolean gcAndCheckGarbage() {
@@ -586,33 +590,18 @@ public class GarbageMonitor implements Dumpable {
         }
     }
 
-    private class BackgroundHeapCheckHandler extends Handler {
-        BackgroundHeapCheckHandler(Looper onLooper) {
-            super(onLooper);
-            if (Looper.getMainLooper().equals(onLooper)) {
-                throw new RuntimeException(
-                        "BackgroundHeapCheckHandler may not run on the ui thread");
-            }
+    private void doGarbageInspection(int id) {
+        if (gcAndCheckGarbage()) {
+            mDelayableExecutor.executeDelayed(this::reinspectGarbageAfterGc, 100);
         }
 
-        @Override
-        public void handleMessage(Message m) {
-            switch (m.what) {
-                case DO_GARBAGE_INSPECTION:
-                    if (gcAndCheckGarbage()) {
-                        postDelayed(GarbageMonitor.this::reinspectGarbageAfterGc, 100);
-                    }
+        mMessageRouter.cancelMessages(DO_GARBAGE_INSPECTION);
+        mMessageRouter.sendMessageDelayed(DO_GARBAGE_INSPECTION, GARBAGE_INSPECTION_INTERVAL);
+    }
 
-                    removeMessages(DO_GARBAGE_INSPECTION);
-                    sendEmptyMessageDelayed(DO_GARBAGE_INSPECTION, GARBAGE_INSPECTION_INTERVAL);
-                    break;
-
-                case DO_HEAP_TRACK:
-                    update();
-                    removeMessages(DO_HEAP_TRACK);
-                    sendEmptyMessageDelayed(DO_HEAP_TRACK, HEAP_TRACK_INTERVAL);
-                    break;
-            }
-        }
+    private void doHeapTrack(int id) {
+        update();
+        mMessageRouter.cancelMessages(DO_HEAP_TRACK);
+        mMessageRouter.sendMessageDelayed(DO_HEAP_TRACK, HEAP_TRACK_INTERVAL);
     }
 }
diff --git a/packages/SystemUI/tests/src/com/android/systemui/util/concurrency/MessageRouterImplTest.java b/packages/SystemUI/tests/src/com/android/systemui/util/concurrency/MessageRouterImplTest.java
new file mode 100644
index 0000000000000..78fc6803ea7ec
--- /dev/null
+++ b/packages/SystemUI/tests/src/com/android/systemui/util/concurrency/MessageRouterImplTest.java
@@ -0,0 +1,371 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.systemui.util.concurrency;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.verify;
+
+import android.testing.AndroidTestingRunner;
+
+import androidx.test.filters.SmallTest;
+
+import com.android.systemui.SysuiTestCase;
+import com.android.systemui.util.time.FakeSystemClock;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.InOrder;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+@SmallTest
+@RunWith(AndroidTestingRunner.class)
+public class MessageRouterImplTest extends SysuiTestCase {
+    private static final int MESSAGE_A = 0;
+    private static final int MESSAGE_B = 1;
+    private static final int MESSAGE_C = 2;
+
+    private static final String METADATA_A = "A";
+    private static final String METADATA_B = "B";
+    private static final String METADATA_C = "C";
+    private static final Foobar METADATA_FOO = new Foobar();
+
+    FakeExecutor mFakeExecutor = new FakeExecutor(new FakeSystemClock());
+    @Mock
+    MessageRouter.SimpleMessageListener mNoMdListener;
+    @Mock
+    MessageRouter.DataMessageListener<String> mStringListener;
+    @Mock
+    MessageRouter.DataMessageListener<Foobar> mFoobarListener;
+    private MessageRouterImpl mMR;
+
+    @Before
+    public void setup() {
+        MockitoAnnotations.initMocks(this);
+        mMR = new MessageRouterImpl(mFakeExecutor);
+    }
+
+    @Test
+    public void testSingleMessage_NoMetaData() {
+        mMR.subscribeTo(MESSAGE_A, mNoMdListener);
+
+        mMR.sendMessage(MESSAGE_A);
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener).onMessage(MESSAGE_A);
+    }
+
+    @Test
+    public void testSingleMessage_WithMetaData() {
+        mMR.subscribeTo(String.class, mStringListener);
+
+        mMR.sendMessage(METADATA_A);
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener).onMessage(METADATA_A);
+    }
+
+    @Test
+    public void testMessages_WithMixedMetaData() {
+        mMR.subscribeTo(String.class, mStringListener);
+        mMR.subscribeTo(Foobar.class, mFoobarListener);
+
+        mMR.sendMessage(METADATA_A);
+        verify(mStringListener, never()).onMessage(anyString());
+        verify(mFoobarListener, never()).onMessage(any(Foobar.class));
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener).onMessage(METADATA_A);
+        verify(mFoobarListener, never()).onMessage(any(Foobar.class));
+
+        reset(mStringListener);
+        reset(mFoobarListener);
+
+        mMR.sendMessage(METADATA_FOO);
+        verify(mStringListener, never()).onMessage(anyString());
+        verify(mFoobarListener, never()).onMessage(any(Foobar.class));
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener, never()).onMessage(anyString());
+        verify(mFoobarListener).onMessage(METADATA_FOO);
+    }
+
+    @Test
+    public void testMessages_WithAndWithoutMetaData() {
+        mMR.subscribeTo(MESSAGE_A, mNoMdListener);
+        mMR.subscribeTo(String.class, mStringListener);
+
+        mMR.sendMessage(MESSAGE_A);
+        verify(mNoMdListener, never()).onMessage(anyInt());
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener).onMessage(MESSAGE_A);
+        verify(mStringListener, never()).onMessage(anyString());
+
+        reset(mNoMdListener);
+        reset(mStringListener);
+
+        mMR.sendMessage(METADATA_A);
+        verify(mNoMdListener, never()).onMessage(anyInt());
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener, never()).onMessage(anyInt());
+        verify(mStringListener).onMessage(METADATA_A);
+    }
+
+    @Test
+    public void testRepeatedMessage() {
+        mMR.subscribeTo(String.class, mStringListener);
+
+        mMR.sendMessage(METADATA_A);
+        mMR.sendMessage(METADATA_A);
+        mMR.sendMessage(METADATA_B);
+        verify(mStringListener, never()).onMessage(anyString());
+
+        InOrder ordered = inOrder(mStringListener);
+        mFakeExecutor.runNextReady();
+        ordered.verify(mStringListener).onMessage(METADATA_A);
+        mFakeExecutor.runNextReady();
+        ordered.verify(mStringListener).onMessage(METADATA_A);
+        mFakeExecutor.runNextReady();
+        ordered.verify(mStringListener).onMessage(METADATA_B);
+    }
+
+    @Test
+    public void testCancelMessage() {
+        mMR.subscribeTo(MESSAGE_A, mNoMdListener);
+        mMR.subscribeTo(MESSAGE_B, mNoMdListener);
+        mMR.subscribeTo(MESSAGE_C, mNoMdListener);
+
+        mMR.sendMessage(MESSAGE_A);
+        mMR.sendMessage(MESSAGE_B);
+        mMR.sendMessage(MESSAGE_B);
+        mMR.sendMessage(MESSAGE_B);
+        mMR.sendMessage(MESSAGE_B);
+        mMR.sendMessage(MESSAGE_C);
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mMR.cancelMessages(MESSAGE_B);
+
+        mFakeExecutor.runAllReady();
+
+        InOrder ordered = inOrder(mNoMdListener);
+        ordered.verify(mNoMdListener).onMessage(MESSAGE_A);
+        ordered.verify(mNoMdListener).onMessage(MESSAGE_C);
+    }
+
+    @Test
+    public void testSendMessage_NoSubscriber() {
+        mMR.sendMessage(MESSAGE_A);
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mMR.subscribeTo(MESSAGE_A, mNoMdListener);
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mMR.sendMessage(MESSAGE_A);
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener).onMessage(MESSAGE_A);
+    }
+
+    @Test
+    public void testUnsubscribe_SpecificMessage_NoMetadata() {
+        mMR.subscribeTo(MESSAGE_A, mNoMdListener);
+        mMR.subscribeTo(MESSAGE_B, mNoMdListener);
+        mMR.sendMessage(MESSAGE_A);
+        mMR.sendMessage(MESSAGE_B);
+
+        mFakeExecutor.runAllReady();
+        InOrder ordered = inOrder(mNoMdListener);
+        ordered.verify(mNoMdListener).onMessage(MESSAGE_A);
+        ordered.verify(mNoMdListener).onMessage(MESSAGE_B);
+
+        reset(mNoMdListener);
+        mMR.unsubscribeFrom(MESSAGE_A, mNoMdListener);
+        mMR.sendMessage(MESSAGE_A);
+        mMR.sendMessage(MESSAGE_B);
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener, never()).onMessage(MESSAGE_A);
+        verify(mNoMdListener).onMessage(MESSAGE_B);
+    }
+
+    @Test
+    public void testUnsubscribe_SpecificMessage_WithMetadata() {
+        mMR.subscribeTo(String.class, mStringListener);
+        mMR.subscribeTo(Foobar.class, mFoobarListener);
+        mMR.sendMessage(METADATA_A);
+        mMR.sendMessage(METADATA_FOO);
+
+        mFakeExecutor.runNextReady();
+        verify(mStringListener).onMessage(METADATA_A);
+        mFakeExecutor.runNextReady();
+        verify(mFoobarListener).onMessage(METADATA_FOO);
+
+        reset(mStringListener);
+        reset(mFoobarListener);
+        mMR.unsubscribeFrom(String.class, mStringListener);
+        mMR.sendMessage(METADATA_A);
+        mMR.sendMessage(METADATA_FOO);
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener, never()).onMessage(METADATA_A);
+        verify(mFoobarListener).onMessage(METADATA_FOO);
+    }
+
+    @Test
+    public void testUnsubscribe_AllMessages_NoMetadata() {
+        mMR.subscribeTo(MESSAGE_A, mNoMdListener);
+        mMR.subscribeTo(MESSAGE_B, mNoMdListener);
+        mMR.subscribeTo(MESSAGE_C, mNoMdListener);
+
+        mMR.sendMessage(MESSAGE_A);
+        mMR.sendMessage(MESSAGE_B);
+        mMR.sendMessage(MESSAGE_C);
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener).onMessage(MESSAGE_A);
+        verify(mNoMdListener).onMessage(MESSAGE_B);
+        verify(mNoMdListener).onMessage(MESSAGE_C);
+
+        reset(mNoMdListener);
+
+        mMR.unsubscribeFrom(mNoMdListener);
+        mMR.sendMessage(MESSAGE_A);
+        mMR.sendMessage(MESSAGE_B);
+        mMR.sendMessage(MESSAGE_C);
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener, never()).onMessage(MESSAGE_A);
+        verify(mNoMdListener, never()).onMessage(MESSAGE_B);
+        verify(mNoMdListener, never()).onMessage(MESSAGE_C);
+    }
+
+    @Test
+    public void testUnsubscribe_AllMessages_WithMetadata() {
+        mMR.subscribeTo(String.class, mStringListener);
+
+        mMR.sendMessage(METADATA_A);
+        mMR.sendMessage(METADATA_B);
+        mMR.sendMessage(METADATA_C);
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener).onMessage(METADATA_A);
+        verify(mStringListener).onMessage(METADATA_B);
+        verify(mStringListener).onMessage(METADATA_C);
+
+        reset(mStringListener);
+
+        mMR.unsubscribeFrom(mStringListener);
+        mMR.sendMessage(METADATA_A);
+        mMR.sendMessage(METADATA_B);
+        mMR.sendMessage(METADATA_C);
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener, never()).onMessage(METADATA_A);
+        verify(mStringListener, never()).onMessage(METADATA_B);
+        verify(mStringListener, never()).onMessage(METADATA_C);
+    }
+
+    @Test
+    public void testSingleDelayedMessage_NoMetaData() {
+        mMR.subscribeTo(MESSAGE_A, mNoMdListener);
+
+        mMR.sendMessageDelayed(MESSAGE_A, 100);
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener, never()).onMessage(anyInt());
+
+        mFakeExecutor.advanceClockToNext();
+        mFakeExecutor.runAllReady();
+        verify(mNoMdListener).onMessage(MESSAGE_A);
+    }
+
+    @Test
+    public void testSingleDelayedMessage_WithMetaData() {
+        mMR.subscribeTo(String.class, mStringListener);
+
+        mMR.sendMessageDelayed(METADATA_C, 1000);
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.advanceClockToNext();
+        mFakeExecutor.runAllReady();
+        verify(mStringListener).onMessage(METADATA_C);
+    }
+
+    @Test
+    public void testMultipleDelayedMessages() {
+        mMR.subscribeTo(String.class, mStringListener);
+
+        mMR.sendMessageDelayed(METADATA_A, 100);
+        mMR.sendMessageDelayed(METADATA_B, 1000);
+        mMR.sendMessageDelayed(METADATA_C, 500);
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.advanceClockToLast();
+        mFakeExecutor.runAllReady();
+
+        InOrder ordered = inOrder(mStringListener);
+        ordered.verify(mStringListener).onMessage(METADATA_A);
+        ordered.verify(mStringListener).onMessage(METADATA_C);
+        ordered.verify(mStringListener).onMessage(METADATA_B);
+    }
+
+    @Test
+    public void testCancelDelayedMessages() {
+        mMR.subscribeTo(String.class, mStringListener);
+
+        mMR.sendMessageDelayed(METADATA_A, 100);
+        mMR.sendMessageDelayed(METADATA_B, 1000);
+        mMR.sendMessageDelayed(METADATA_C, 500);
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mFakeExecutor.runAllReady();
+        verify(mStringListener, never()).onMessage(anyString());
+
+        mMR.cancelMessages(String.class);
+        mFakeExecutor.advanceClockToLast();
+        mFakeExecutor.runAllReady();
+
+        verify(mStringListener, never()).onMessage(anyString());
+    }
+
+    private static class Foobar {}
+}
diff --git a/packages/SystemUI/tests/src/com/android/systemui/util/leak/GarbageMonitorTest.java b/packages/SystemUI/tests/src/com/android/systemui/util/leak/GarbageMonitorTest.java
index bcc20c2d1b378..724d14e203745 100644
--- a/packages/SystemUI/tests/src/com/android/systemui/util/leak/GarbageMonitorTest.java
+++ b/packages/SystemUI/tests/src/com/android/systemui/util/leak/GarbageMonitorTest.java
@@ -17,124 +17,94 @@
 package com.android.systemui.util.leak;
 
 import static org.mockito.ArgumentMatchers.anyInt;
-import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
-import android.content.Context;
-import android.os.Looper;
 import android.testing.AndroidTestingRunner;
-import android.testing.TestableLooper;
-import android.testing.TestableLooper.RunWithLooper;
 
 import androidx.test.filters.SmallTest;
 
 import com.android.systemui.SysuiTestCase;
+import com.android.systemui.util.concurrency.FakeExecutor;
+import com.android.systemui.util.concurrency.MessageRouterImpl;
+import com.android.systemui.util.time.FakeSystemClock;
 
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
 
 @SmallTest
 @RunWith(AndroidTestingRunner.class)
-@RunWithLooper
 public class GarbageMonitorTest extends SysuiTestCase {
 
-    private LeakReporter mLeakReporter;
-    private TrackedGarbage mTrackedGarbage;
-    private TestableGarbageMonitor mGarbageMonitor;
+    @Mock private LeakReporter mLeakReporter;
+    @Mock private TrackedGarbage mTrackedGarbage;
+    private GarbageMonitor mGarbageMonitor;
+    private final FakeExecutor mFakeExecutor = new FakeExecutor(new FakeSystemClock());
 
     @Before
     public void setup() {
-        mTrackedGarbage = mock(TrackedGarbage.class);
-        mLeakReporter = mock(LeakReporter.class);
+        MockitoAnnotations.initMocks(this);
         mGarbageMonitor =
-                new TestableGarbageMonitor(
+                new GarbageMonitor(
                         mContext,
-                        TestableLooper.get(this).getLooper(),
+                        mFakeExecutor,
+                        new MessageRouterImpl(mFakeExecutor),
                         new LeakDetector(null, mTrackedGarbage, null),
                         mLeakReporter);
     }
 
-    @Test
-    public void testCallbacks_getScheduled() {
-        mGarbageMonitor.startLeakMonitor();
-        mGarbageMonitor.runCallbacksOnce();
-        mGarbageMonitor.runCallbacksOnce();
-        mGarbageMonitor.runCallbacksOnce();
-    }
-
-    @Test
-    public void testNoGarbage_doesntDump() {
-        when(mTrackedGarbage.countOldGarbage()).thenReturn(0);
-
-        mGarbageMonitor.startLeakMonitor();
-        mGarbageMonitor.runCallbacksOnce();
-        mGarbageMonitor.runCallbacksOnce();
-        mGarbageMonitor.runCallbacksOnce();
-
-        verify(mLeakReporter, never()).dumpLeak(anyInt());
-    }
-
     @Test
     public void testALittleGarbage_doesntDump() {
-        when(mTrackedGarbage.countOldGarbage()).thenReturn(4);
+        when(mTrackedGarbage.countOldGarbage()).thenReturn(GarbageMonitor.GARBAGE_ALLOWANCE);
 
-        mGarbageMonitor.startLeakMonitor();
-        mGarbageMonitor.runCallbacksOnce();
-        mGarbageMonitor.runCallbacksOnce();
-        mGarbageMonitor.runCallbacksOnce();
+        mGarbageMonitor.reinspectGarbageAfterGc();
 
         verify(mLeakReporter, never()).dumpLeak(anyInt());
     }
 
     @Test
     public void testTransientGarbage_doesntDump() {
-        when(mTrackedGarbage.countOldGarbage()).thenReturn(100);
+        when(mTrackedGarbage.countOldGarbage()).thenReturn(GarbageMonitor.GARBAGE_ALLOWANCE + 1);
 
+        // Start the leak monitor. Nothing gets reported immediately.
         mGarbageMonitor.startLeakMonitor();
-        mGarbageMonitor.runInspectCallback();
+        mFakeExecutor.runAllReady();
+        verify(mLeakReporter, never()).dumpLeak(anyInt());
 
+        // Garbage gets reset to 0 before the leak reporte actually gets called.
         when(mTrackedGarbage.countOldGarbage()).thenReturn(0);
+        mFakeExecutor.advanceClockToLast();
+        mFakeExecutor.runAllReady();
 
-        mGarbageMonitor.runReinspectCallback();
-
+        // Therefore nothing gets dumped.
         verify(mLeakReporter, never()).dumpLeak(anyInt());
     }
 
     @Test
     public void testLotsOfPersistentGarbage_dumps() {
-        when(mTrackedGarbage.countOldGarbage()).thenReturn(100);
+        when(mTrackedGarbage.countOldGarbage()).thenReturn(GarbageMonitor.GARBAGE_ALLOWANCE + 1);
 
-        mGarbageMonitor.startLeakMonitor();
-        mGarbageMonitor.runCallbacksOnce();
+        mGarbageMonitor.reinspectGarbageAfterGc();
 
-        verify(mLeakReporter).dumpLeak(anyInt());
+        verify(mLeakReporter).dumpLeak(GarbageMonitor.GARBAGE_ALLOWANCE + 1);
     }
 
-    private static class TestableGarbageMonitor extends GarbageMonitor {
-        public TestableGarbageMonitor(
-                Context context,
-                Looper looper,
-                LeakDetector leakDetector,
-                LeakReporter leakReporter) {
-            super(context, looper, leakDetector, leakReporter);
-        }
+    @Test
+    public void testLotsOfPersistentGarbage_dumpsAfterAtime() {
+        when(mTrackedGarbage.countOldGarbage()).thenReturn(GarbageMonitor.GARBAGE_ALLOWANCE + 1);
 
-        void runInspectCallback() {
-            startLeakMonitor();
-        }
+        // Start the leak monitor. Nothing gets reported immediately.
+        mGarbageMonitor.startLeakMonitor();
+        mFakeExecutor.runAllReady();
+        verify(mLeakReporter, never()).dumpLeak(anyInt());
 
-        void runReinspectCallback() {
-            reinspectGarbageAfterGc();
-        }
+        mFakeExecutor.advanceClockToLast();
+        mFakeExecutor.runAllReady();
 
-        void runCallbacksOnce() {
-            // Note that TestableLooper doesn't currently support delayed messages so we need to run
-            // callbacks explicitly.
-            runInspectCallback();
-            runReinspectCallback();
-        }
+        verify(mLeakReporter).dumpLeak(GarbageMonitor.GARBAGE_ALLOWANCE + 1);
     }
 }
\ No newline at end of file