Adjust volume bar visibility in HDMI-CEC system audio mode

When HDMI-CEC system audio mode is activated.
1. Hide volume bar when volume button is pressed in TV
2. Show volume bar when TV receives volume notification from
   Audio Receiver.

Otherwise, (system audio mode off) follows normal TV's behavior.

Bug: 17347499

Change-Id: I1f5bc14285d60d8626a8fbbef9e1959cae7d193b
diff --git a/media/java/android/media/AudioService.java b/media/java/android/media/AudioService.java
index 40d45ea..71a05ab 100644
--- a/media/java/android/media/AudioService.java
+++ b/media/java/android/media/AudioService.java
@@ -1351,6 +1351,16 @@
             streamType = AudioSystem.STREAM_NOTIFICATION;
         }
 
+        // If Hdmi-CEC system audio mode is on, show volume bar
+        // only when TV receives volume notification from Audio Receiver.
+        if (mHdmiTvClient != null && streamType == AudioSystem.STREAM_MUSIC) {
+            synchronized (mHdmiTvClient) {
+                if (mHdmiSystemAudioSupported &&
+                        ((flags & AudioManager.FLAG_HDMI_SYSTEM_AUDIO_VOLUME) == 0)) {
+                    flags &= ~AudioManager.FLAG_SHOW_UI;
+                }
+            }
+        }
         mVolumeController.postVolumeChanged(streamType, flags);
 
         if ((flags & AudioManager.FLAG_FIXED_VOLUME) == 0) {