Add a BufferItem parameter to onFrameAvailable

Passes the BufferItem for the queued buffer to the onFrameAvailable
callback so the consumer can track the BufferQueue's contents. Also
adds an onFrameReplaced callback, which is necessary if the consumer
wants to do anything more than simple queue length tracking.

Bug: 18111837
Change-Id: If9d07229c9b586c668e5f99074e9b63b0468feb0