AudioService: persist volume of ring stream when ringer mode changed

-Originally, when ringer mode changed from vibrate to normal by
 adjusting volume from 0 to 1 , volume index will not be persisted.
 After device rebooted, volume of ring stream will be restored to 0
-Persist volume index when ringer mode changed

Bug: 18762217

Change-Id: I75fbeaab01d80b8bcee623795f59a9e9f16b9634
diff --git a/services/core/java/com/android/server/audio/AudioService.java b/services/core/java/com/android/server/audio/AudioService.java
index eaece09..ed9460b 100644
--- a/services/core/java/com/android/server/audio/AudioService.java
+++ b/services/core/java/com/android/server/audio/AudioService.java
@@ -1920,6 +1920,15 @@
                                 entry.setValue(10);
                             }
                         }
+                        // Persist volume for stream ring when it is changed here
+                      final int device = getDeviceForStream(streamType);
+                      sendMsg(mAudioHandler,
+                              MSG_PERSIST_VOLUME,
+                              SENDMSG_QUEUE,
+                              device,
+                              0,
+                              mStreamStates[streamType],
+                              PERSIST_DELAY);
                     }
                 }
                 mStreamStates[streamType].mute(false);