Use size_t for frame size

except in the control block, where we don't have room.

In AudioFlinger::ThreadBase::TrackBase::getBuffer,
read the frame size from control block only once.

Change-Id: Id6c4bccd4ed3e07d91df6bbea43bae45524f9f4e
diff --git a/include/private/media/AudioTrackShared.h b/include/private/media/AudioTrackShared.h
index 046d5e9..b661cb9 100644
--- a/include/private/media/AudioTrackShared.h
+++ b/include/private/media/AudioTrackShared.h
@@ -80,7 +80,7 @@
                 // 8 bit PCM data: in this case,  mCblk->frameSize is based on a sample size of
                 // 16 bit because data is converted to 16 bit before being stored in buffer
 
-                uint8_t     frameSize;
+                uint8_t     frameSize;       // would normally be size_t, but 8 bits is plenty
                 uint8_t     pad1;
                 uint16_t    bufferTimeoutMs; // Maximum cumulated timeout before restarting audioflinger