Remove support for audio renderers to disable themselves at run time.

UMA data tells us this code path is rarely hit (~0.01% on stable). It
also complicates a lot of media pipeline/demuxer logic. Replace all of
it with an error callback.

BUG=234708

Review URL: https://codereview.chromium.org/270223002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269368 0039d316-1c4b-4281-b951-d872f2087c98

• media/base/audio_renderer.h[diff]
• media/base/demuxer.h[diff]
• media/base/media_log.cc[diff]
• media/base/media_log_event.h[diff]
• media/base/mock_filters.h[diff]
• media/base/pipeline.cc[diff]
• media/base/pipeline.h[diff]
• media/base/pipeline_unittest.cc[diff]
• media/filters/audio_renderer_impl.cc[diff]
• media/filters/audio_renderer_impl.h[diff]
• media/filters/audio_renderer_impl_unittest.cc[diff]
• media/filters/chunk_demuxer.cc[diff]
• media/filters/chunk_demuxer.h[diff]
• media/filters/chunk_demuxer_unittest.cc[diff]
• media/filters/ffmpeg_demuxer.cc[diff]
• media/filters/ffmpeg_demuxer.h[diff]
• media/filters/ffmpeg_demuxer_unittest.cc[diff]