Zero out return values in media binder calls

More specifically when handling:
* GET_STREAM_VOLUME in IAudioPolicyService, and
* GET_CURRENT_POSITION and GET_DURATION in IMediaPlayer

This prevents leaking uninitialized values across binder in error cases.

Bug: 23756261
Change-Id: I0ffd900ab12b685b0611259ade4a3efb1ec5defe
(cherry picked from commit 8923543)

Author: rjsh

media/libmedia/IAudioPolicyService.cpp

@@ -566,7 +566,7 @@ status_t BnAudioPolicyService::onTransact(
             audio_stream_type_t stream =
                     static_cast <audio_stream_type_t>(data.readInt32());
             audio_devices_t device = static_cast <audio_devices_t>(data.readInt32());
-            int index;
+            int index = 0;
             status_t status = getStreamVolumeIndex(stream, &index, device);
             reply->writeInt32(index);
             reply->writeInt32(static_cast <uint32_t>(status));

media/libmedia/IMediaPlayer.cpp

@@ -423,15 +423,15 @@ status_t BnMediaPlayer::onTransact(
         } break;
         case GET_CURRENT_POSITION: {
             CHECK_INTERFACE(IMediaPlayer, data, reply);
-            int msec;
+            int msec = 0;
             status_t ret = getCurrentPosition(&msec);
             reply->writeInt32(msec);
             reply->writeInt32(ret);
             return NO_ERROR;
         } break;
         case GET_DURATION: {
             CHECK_INTERFACE(IMediaPlayer, data, reply);
-            int msec;
+            int msec = 0;
             status_t ret = getDuration(&msec);
             reply->writeInt32(msec);
             reply->writeInt32(ret);