Use the suggested stream if it's currently active

This makes the MediaSessionService check if the suggested stream is active
when dispatching a volume event and prefer it to a remote session if it is.
This mostly affects apps that use Activity.setVolumeControlStream.

bug:18318480
Change-Id: Ib8825394bf7a223fbd92bcb2c3ecb7c596ce7c29

services/core/java/com/android/server/media/MediaSessionService.java

@@ -805,7 +805,12 @@ public class MediaSessionService extends SystemService implements Monitor {
                         + flags + ", suggestedStream=" + suggestedStream);
 
             }
-            if (session == null) {
+            boolean preferSuggestedStream = false;
+            if (isValidLocalStreamType(suggestedStream)
+                    && AudioSystem.isStreamActive(suggestedStream, 0)) {
+                preferSuggestedStream = true;
+            }
+            if (session == null || preferSuggestedStream) {
                 if ((flags & AudioManager.FLAG_ACTIVE_MEDIA_ONLY) != 0
                         && !AudioSystem.isStreamActive(AudioManager.STREAM_MUSIC, 0)) {
                     if (DEBUG) {
@@ -959,6 +964,12 @@ public class MediaSessionService extends SystemService implements Monitor {
             return keyCode == KeyEvent.KEYCODE_HEADSETHOOK;
         }
 
+        // we only handle public stream types, which are 0-5
+        private boolean isValidLocalStreamType(int streamType) {
+            return streamType >= AudioManager.STREAM_VOICE_CALL
+                    && streamType <= AudioManager.STREAM_NOTIFICATION;
+        }
+
         private KeyEventWakeLockReceiver mKeyEventReceiver = new KeyEventWakeLockReceiver(mHandler);
 
         class KeyEventWakeLockReceiver extends ResultReceiver implements Runnable,