Volume keys control music volume after music stops

On phones, add a short delay during which volume keys still
control music volume after music has stopped. This is similar
to the tablet behavior for notifications volume.
It allows users to control the prompt volume for talk back,
voice search or navigation even after the prompt has stopped.

Bug 7162364.

Change-Id: Iffbca9ec30ebcbe5846f783ddd260b6e736caf2b

Author: Eric Laurent

media/java/android/media/AudioService.java

@@ -387,9 +387,11 @@ public void onError(int error) {
     private Looper mSoundPoolLooper = null;
     // volume applied to sound played with playSoundEffect()
     private static int sSoundEffectVolumeDb;
-    // getActiveStreamType() will return STREAM_NOTIFICATION during this period after a notification
+    // getActiveStreamType() will return:
+    // - STREAM_NOTIFICATION on tablets during this period after a notification stopped
+    // - STREAM_MUSIC on phones during this period after music or talkback/voice search prompt
     // stopped
-    private static final int NOTIFICATION_VOLUME_DELAY_MS = 5000;
+    private static final int DEFAULT_STREAM_TYPE_OVERRIDE_DELAY_MS = 5000;
     // previous volume adjustment direction received by checkForRingerModeChange()
     private int mPrevVolDirection = AudioManager.ADJUST_SAME;
     // Keyguard manager proxy
@@ -2340,7 +2342,8 @@ private int getActiveStreamType(int suggestedStreamType) {
                     if (DEBUG_VOL)
                         Log.v(TAG, "getActiveStreamType: Forcing STREAM_REMOTE_MUSIC");
                     return STREAM_REMOTE_MUSIC;
-                } else if (AudioSystem.isStreamActive(AudioSystem.STREAM_MUSIC, 0)) {
+                } else if (AudioSystem.isStreamActive(AudioSystem.STREAM_MUSIC,
+                            DEFAULT_STREAM_TYPE_OVERRIDE_DELAY_MS)) {
                     if (DEBUG_VOL)
                         Log.v(TAG, "getActiveStreamType: Forcing STREAM_MUSIC stream active");
                     return AudioSystem.STREAM_MUSIC;
@@ -2369,9 +2372,9 @@ private int getActiveStreamType(int suggestedStreamType) {
                     return AudioSystem.STREAM_VOICE_CALL;
                 }
             } else if (AudioSystem.isStreamActive(AudioSystem.STREAM_NOTIFICATION,
-                    NOTIFICATION_VOLUME_DELAY_MS) ||
+                    DEFAULT_STREAM_TYPE_OVERRIDE_DELAY_MS) ||
                     AudioSystem.isStreamActive(AudioSystem.STREAM_RING,
-                            NOTIFICATION_VOLUME_DELAY_MS)) {
+                            DEFAULT_STREAM_TYPE_OVERRIDE_DELAY_MS)) {
                 if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Forcing STREAM_NOTIFICATION");
                 return AudioSystem.STREAM_NOTIFICATION;
             } else if (suggestedStreamType == AudioManager.USE_DEFAULT_STREAM_TYPE) {