GitLab

- Consolidates FFmpegAudioDecoder and OpusAudioDecoder unittests
since they were identical anyways.
- Extends the AudioFileReader unittests to perform packet consistency
checks between seeks.
- Extends the new consolidated tests for WAV, FLAC, MP3, and AAC.
- Adds decoded output consistency checks using MD5 for all files.
- Removes old tests which end up duplicating efforts.
- Expands tests for bad decoder configs and buffers w/o timestamps.
- Expands tests to include AudioDiscardHelper usage.

BUG=381356
TEST=shiny new tests!

Review URL: https://codereview.chromium.org/311373004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278667 0039d316-1c4b-4281-b951-d872f2087c98