Stop scan on device chooser activity backgrounded

This effectively treats chooser activity pause event as cancel.

Bug: 30932767
Test: Install two toy apps and call associate API from both.
  Ensure foreground app always end up showing fresh data.
Change-Id: I49943959c2b4f05f2e1d49603fd472b3e0c47213

core/java/android/companion/ICompanionDeviceDiscoveryServiceCallback.aidl

@@ -19,4 +19,5 @@ package android.companion;
 /** @hide */
 interface ICompanionDeviceDiscoveryServiceCallback {
     oneway void onDeviceSelected(String packageName, int userId, String deviceAddress);
+    oneway void onDeviceSelectionCancel();
 }

packages/CompanionDeviceManager/src/com/android/companiondevicemanager/DeviceChooserActivity.java

@@ -79,15 +79,25 @@ public class DeviceChooserActivity extends Activity {
         }
 
         mPairButton = findViewById(R.id.button_pair);
-        mPairButton.setOnClickListener((view) ->
-                onPairTapped(getService().mSelectedDevice));
+        mPairButton.setOnClickListener(v -> onPairTapped(getService().mSelectedDevice));
         updatePairButtonEnabled();
 
         mCancelButton = findViewById(R.id.button_cancel);
-        mCancelButton.setOnClickListener((view) -> {
-            setResult(RESULT_CANCELED);
-            finish();
-        });
+        mCancelButton.setOnClickListener(v -> cancel());
+    }
+
+    private void cancel() {
+        getService().onCancel();
+        setResult(RESULT_CANCELED);
+        finish();
+    }
+
+    @Override
+    protected void onPause() {
+        super.onPause();
+        if (!isFinishing()) {
+            cancel();
+        }
     }
 
     private CharSequence getCallingAppName() {

packages/CompanionDeviceManager/src/com/android/companiondevicemanager/DeviceDiscoveryService.java

@@ -202,8 +202,6 @@ public class DeviceDiscoveryService extends Service {
             reset();
         } else if (DEBUG) Log.i(LOG_TAG, "startDiscovery: duplicate request: " + request);
 
-
-
         if (!ArrayUtils.isEmpty(mDevicesFound)) {
             onReadyToShowUI();
         }
@@ -307,6 +305,14 @@ public class DeviceDiscoveryService extends Service {
         }
     }
 
+    void onCancel() {
+        try {
+            mServiceCallback.onDeviceSelectionCancel();
+        } catch (RemoteException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     class DevicesAdapter extends ArrayAdapter<DeviceFilterPair> {
         //TODO wifi icon
         private Drawable BLUETOOTH_ICON = icon(android.R.drawable.stat_sys_data_bluetooth);

services/print/java/com/android/server/print/CompanionDeviceManagerService.java

@@ -135,10 +135,10 @@ public class CompanionDeviceManagerService extends SystemService implements Bind
 
     @Override
     public void binderDied() {
-        Handler.getMain().post(this::handleBinderDied);
+        Handler.getMain().post(this::cleanup);
     }
 
-    private void handleBinderDied() {
+    private void cleanup() {
         mServiceConnection = unbind(mServiceConnection);
         mFindDeviceCallback = unlinkToDeath(mFindDeviceCallback, this, 0);
     }
@@ -201,7 +201,6 @@ public class CompanionDeviceManagerService extends SystemService implements Bind
             }
         }
 
-
         @Override
         public List<String> getAssociations(String callingPackage) {
             return CollectionUtils.map(
@@ -237,7 +236,7 @@ public class CompanionDeviceManagerService extends SystemService implements Bind
                     mFindDeviceCallback.asBinder().linkToDeath(
                             CompanionDeviceManagerService.this, 0);
                 } catch (RemoteException e) {
-                    handleBinderDied();
+                    cleanup();
                     return;
                 }
                 try {
@@ -266,10 +265,16 @@ public class CompanionDeviceManagerService extends SystemService implements Bind
 
             @Override
             public void onDeviceSelected(String packageName, int userId, String deviceAddress) {
-                //TODO unbind
                 updateSpecialAccessPermissionForAssociatedPackage(packageName, userId);
                 recordAssociation(packageName, deviceAddress);
+                cleanup();
             }
+
+            @Override
+            public void onDeviceSelectionCancel() {
+                cleanup();
+            }
+
         };
     }