The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/32a6c13991b642c992f9879bb808c527bc6dc278

commit 32a6c13991b642c992f9879bb808c527bc6dc278
Author: dalecurtis <dalecurtis@chromium.org>
Date: Mon Apr 17 20:32:08 2017

Only run container name detection upon ffmpeg parse failure.

If ffmpeg thinks it can demux the file, we should defer to its result
instead of trying to compute our own. This avoids any unnecessary delay
in playback of supported formats by only running our checks if ffmpeg
indicates it can't demux the content.

BUG= 711781 
TEST=new unittests

Review-Url: https://codereview.chromium.org/2819863003
Cr-Commit-Position: refs/heads/master@{#465003}

[modify] https://crrev.com/32a6c13991b642c992f9879bb808c527bc6dc278/media/base/container_names.cc
[modify] https://crrev.com/32a6c13991b642c992f9879bb808c527bc6dc278/media/base/container_names.h
[modify] https://crrev.com/32a6c13991b642c992f9879bb808c527bc6dc278/media/filters/ffmpeg_glue.cc
[modify] https://crrev.com/32a6c13991b642c992f9879bb808c527bc6dc278/media/filters/ffmpeg_glue_unittest.cc
[add] https://crrev.com/32a6c13991b642c992f9879bb808c527bc6dc278/media/test/data/bear.amr

Since M59 went stable (end of May) the unknown container rate has dropped to less than 5% (was 45-50% since the end of March). Since this looks reasonable, marking this as fixed.

Unknown containers started dropping after M58 release. Latest results (7-Nov) are 1.7%, been below 5% since M60 shipped.