Begin refactor of AVDA to support zero-copy.

Refactor AndroidVideoDecodeAccelerator into a class that manages the MediaCodec buffers, but delegates handling the SurfaceTexture to BackingStrategy implementations.  The AndroidCopyingBackingStrategy class implements the texture copy into the picture buffer, as it did in previous versions.

BUG=507834

Review URL: https://codereview.chromium.org/1313913003

Cr-Commit-Position: refs/heads/master@{#348774}
10 files changed