GitLab

AVDACopyingBackingStrategy is unused so it's now deleted. Since we only have a single
strategy left, it's renamed to AVDAPictureBufferManager, since its role is mostly
to associate PictureBuffers with MediaCodec buffers.

BUG=637463

Review-Url: https://codereview.chromium.org/2296513003
Cr-Commit-Position: refs/heads/master@{#415803}