media: Implement MediaCodecVideoDecoder initialization

This adds initialization logic to MediaCodecVideoDecoder. Most of it
comes from AVDA with some tweaks. It also includes moving
FakeCodecAllocator to its own file for reuse.

Bug: 660942
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ib835ed7fdc263ef321c264978a6185134501ab87
Reviewed-on: https://chromium-review.googlesource.com/509895
Reviewed-by: Frank Liberato <[email protected]>
Commit-Queue: Chris Watkins <[email protected]>
Cr-Commit-Position: refs/heads/master@{#473660}
12 files changed