Indicate screen off condition to audio framework.

Add a mechanism for AudioService to notify audio framework and audio HAL
that screen is turned on or off. This indication can be used by lower
audio layers to trigger low power audio playback mode.
Current implementaiton based on setParameters() method is experimental
and will be replaced by a different interface when ready.

Change-Id: Ie72ada0a8edec3d71b47681b9f51cb5bc839d45b

Author: Eric Laurent

media/java/android/media/AudioService.java

@@ -368,6 +368,8 @@ public AudioService(Context context) {
         intentFilter.addAction(Intent.ACTION_USB_DGTL_HEADSET_PLUG);
         intentFilter.addAction(Intent.ACTION_HDMI_AUDIO_PLUG);
         intentFilter.addAction(Intent.ACTION_BOOT_COMPLETED);
+        intentFilter.addAction(Intent.ACTION_SCREEN_ON);
+        intentFilter.addAction(Intent.ACTION_SCREEN_OFF);
         context.registerReceiver(mReceiver, intentFilter);
 
         // Register for package removal intent broadcasts for media button receiver persistence
@@ -2565,6 +2567,10 @@ public void onReceive(Context context, Intent intent) {
                         removeMediaButtonReceiverForPackage(packageName);
                     }
                 }
+            } else if (action.equals(Intent.ACTION_SCREEN_ON)) {
+                AudioSystem.setParameters("screen_state=on");
+            } else if (action.equals(Intent.ACTION_SCREEN_OFF)) {
+                AudioSystem.setParameters("screen_state=off");
             }
         }
     }