Remove using ServiceManager API in MediaSessionManager

MediaSessionManager calls ServiceManager#getService(string) to get
ISessionManager, but it is a hidden API that will not be made into
@SystemApi (ag/6329675).

Instead, create a wrapper class that can only retrieve specified
media service binders. (ag/10123575 for reference)

Bug: 159955826
Test: atest
    CtsMediaTestCases:android.media.cts.MediaSessionManagerTest
Change-Id: I1ab89d1217e8e3d071b38da772ee96889e9859b1

core/java/android/app/ActivityThread.java

@@ -86,6 +86,8 @@ import android.graphics.Canvas;
 import android.graphics.HardwareRenderer;
 import android.hardware.display.DisplayManagerGlobal;
 import android.inputmethodservice.InputMethodService;
+import android.media.MediaFrameworkInitializer;
+import android.media.MediaServiceManager;
 import android.net.ConnectivityManager;
 import android.net.IConnectivityManager;
 import android.net.Proxy;
@@ -7665,6 +7667,7 @@ public final class ActivityThread extends ClientTransactionHandler {
     public static void initializeMainlineModules() {
         TelephonyFrameworkInitializer.setTelephonyServiceManager(new TelephonyServiceManager());
         StatsFrameworkInitializer.setStatsServiceManager(new StatsServiceManager());
+        MediaFrameworkInitializer.setMediaServiceManager(new MediaServiceManager());
     }
 
     private void purgePendingResources() {

media/java/android/media/MediaFrameworkInitializer.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2020 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 android.media;
+
+import android.annotation.NonNull;
+
+import com.android.internal.util.Preconditions;
+
+import java.util.Objects;
+
+/**
+ * Class for performing registration for all media services
+ *
+ * TODO (b/160513103): Move this class when moving media service code to APEX
+ * @hide
+ */
+public class MediaFrameworkInitializer {
+    private MediaFrameworkInitializer() {
+    }
+
+    private static volatile MediaServiceManager sMediaServiceManager;
+
+    /**
+     * Sets an instance of {@link MediaServiceManager} that allows
+     * the media mainline module to register/obtain media binder services. This is called
+     * by the platform during the system initialization.
+     *
+     * @param mediaServiceManager instance of {@link MediaServiceManager} that allows
+     * the media mainline module to register/obtain media binder services.
+     */
+    public static void setMediaServiceManager(
+            @NonNull MediaServiceManager mediaServiceManager) {
+        Preconditions.checkState(sMediaServiceManager == null,
+                "setMediaServiceManager called twice!");
+        sMediaServiceManager = Objects.requireNonNull(mediaServiceManager);
+    }
+
+    /** @hide */
+    public static MediaServiceManager getMediaServiceManager() {
+        return sMediaServiceManager;
+    }
+}

media/java/android/media/MediaServiceManager.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2020 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 android.media;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.os.IBinder;
+import android.os.ServiceManager;
+
+/**
+ * Provides a way to register and obtain the system service binder objects managed by the media
+ * service.
+ *
+ * <p> Only the media mainline module will be able to access an instance of this class.
+ * @hide
+ */
+public class MediaServiceManager {
+    /**
+     * @hide
+     */
+    public MediaServiceManager() {}
+
+    /**
+     * A class that exposes the methods to register and obtain each system service.
+     */
+    public static final class ServiceRegisterer {
+        private final String mServiceName;
+
+        /**
+         * @hide
+         */
+        public ServiceRegisterer(String serviceName) {
+            mServiceName = serviceName;
+        }
+
+        /**
+         * Get the system server binding object for MediaServiceManager.
+         *
+         * <p> This blocks until the service instance is ready.
+         * or a timeout happens, in which case it returns null.
+         */
+        @Nullable
+        public IBinder get() {
+            return ServiceManager.getService(mServiceName);
+        }
+    }
+
+    /**
+     * Returns {@link ServiceRegisterer} for the "media_session" service.
+     */
+    @NonNull
+    public ServiceRegisterer getMediaSessionServiceRegisterer() {
+        return new ServiceRegisterer("media_session");
+    }
+}

media/java/android/media/session/MediaSessionManager.java

@@ -28,14 +28,13 @@ import android.content.Context;
 import android.content.pm.ParceledListSlice;
 import android.media.AudioManager;
 import android.media.IRemoteVolumeController;
+import android.media.MediaFrameworkInitializer;
 import android.media.MediaSession2;
 import android.media.Session2Token;
 import android.os.Bundle;
 import android.os.Handler;
-import android.os.IBinder;
 import android.os.RemoteException;
 import android.os.ResultReceiver;
-import android.os.ServiceManager;
 import android.os.UserHandle;
 import android.service.media.MediaBrowserService;
 import android.service.notification.NotificationListenerService;
@@ -115,8 +114,10 @@ public final class MediaSessionManager {
         // Consider rewriting like DisplayManagerGlobal
         // Decide if we need context
         mContext = context;
-        IBinder b = ServiceManager.getService(Context.MEDIA_SESSION_SERVICE);
-        mService = ISessionManager.Stub.asInterface(b);
+        mService = ISessionManager.Stub.asInterface(MediaFrameworkInitializer
+                .getMediaServiceManager()
+                .getMediaSessionServiceRegisterer()
+                .get());
     }
 
     /**