Ringtone: keep a reference until playback completion.
Ringtone: keep a reference until playback completion.

Keep a reference on active Ringtones to avoid garbage collection
before playback is complete.

Bug: 11366759.
Change-Id: Icb04da427c20e0b4657e9e8b13b3ecab98e5a333

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base