Findit identified the culprit r557832 with confidence 100.0% in the config "chromium.linux / Cast Linux"
based on the flakiness trend:

https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVyyQELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKSAWNocm9taXVtLmxpbnV4L0Nhc3QgTGludXgvNTIzNDEvY29udGVudF91bml0dGVzdHMvVW1WdVpHVnlSbkpoYldWQmRXUnBiMGx1Y0hWMFUzUnlaV0Z0Um1GamRHOXllVlJsYzNRdVEzSmxZWFJsVDNCbGJtVmtVM1J5WldGdFgwWnZjbmRoY21SelEyRnNiQT09DAsSE01hc3RlckZsYWtlQW5hbHlzaXMYAQw


Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).
Feedback is welcome! Please use component Tools>Test>FindIt>Flakiness

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/80cbe682e287f7562c7fd7e7b0a24927de78675d

commit 80cbe682e287f7562c7fd7e7b0a24927de78675d
Author: Findit <findit-for-me@appspot.gserviceaccount.com>
Date: Fri May 11 10:55:25 2018

Revert "Add a new RenderFrameAudioInputStreamFactory"

This reverts commit 539d243b087e6e31281c3229929f5a1fc97cd82f.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 557832 as the
culprit for flakes in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/flake/flake-culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyQwsSDEZsYWtlQ3VscHJpdCIxY2hyb21pdW0vNTM5ZDI0M2IwODdlNmUzMTI4MWMzMjI5OTI5ZjVhMWZjOTdjZDgyZgw

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.linux/Cast%20Linux/None

Sample Failed Step: content_unittests

Sample Failed test: RenderFrameAudioInputStreamFactoryTest.CreateOpenedStream_ForwardsCall

Original change's description:
> Add a new RenderFrameAudioInputStreamFactory
> 
> It checks that the stream is allowed and forwards the request to the
> relevant ForwardingAudioStreamFactory if so. This will cause
> the stream to be served by the audio service.
> The old RenderFrameAudioInputStreamFactory which creates streams
> living in content/ is renamed to
> OldRenderFrameAudioInputStreamFactory. Since the class was renamed,
> the files were moved (by adding "old_" to the beginning). No need to
> review those files. Also note that replacement is diffed against
> the previous implementation. It's probably best to just ignore the diff
> and review render_frame_audio_input_stream_factory{.cc,.h,_unittest.cc}
> as new files.
> 
> The same flag as for output is used to switch between the old factory
> and the new one.
> 
> Approximate diagram of stuff:
> https://docs.google.com/drawings/d/1_ZIKj6lihGKRjq4Mflduitmkn_REqpHFeqVNelBGHHk/edit
> 
> Bug:  830493 ,  836226 
> Change-Id: Ib0f58a52d849a48ba79405f0d499444c66029b58
> Reviewed-on: https://chromium-review.googlesource.com/1050245
> Commit-Queue: Max Morin <maxmorin@chromium.org>
> Reviewed-by: Nasko Oskov <nasko@chromium.org>
> Reviewed-by: Guido Urdaneta <guidou@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#557832}

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  830493 ,  836226 ,  842115 
Flaky step name: content_unittests
Flaky test name: RenderFrameAudioInputStreamFactoryTest.CreateOpenedStream_ForwardsCall

Change-Id: If1683461af7fcbe0a9be633db62087dafe66235b
Reviewed-on: https://chromium-review.googlesource.com/1054162
Cr-Commit-Position: refs/heads/master@{#557838}
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/BUILD.gn
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/frame_host/render_frame_host_impl.cc
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/frame_host/render_frame_host_impl.h
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/renderer_host/media/media_stream_manager.cc
[delete] https://crrev.com/a550e3e2c31893045d97adad488ecb92c5cd76ca/content/browser/renderer_host/media/old_render_frame_audio_input_stream_factory.cc
[delete] https://crrev.com/a550e3e2c31893045d97adad488ecb92c5cd76ca/content/browser/renderer_host/media/old_render_frame_audio_input_stream_factory.h
[delete] https://crrev.com/a550e3e2c31893045d97adad488ecb92c5cd76ca/content/browser/renderer_host/media/old_render_frame_audio_input_stream_factory_unittest.cc
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/renderer_host/media/render_frame_audio_input_stream_factory.cc
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/renderer_host/media/render_frame_audio_input_stream_factory.h
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/renderer_host/media/render_frame_audio_input_stream_factory_unittest.cc
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/browser/renderer_host/render_process_host_impl.cc
[modify] https://crrev.com/80cbe682e287f7562c7fd7e7b0a24927de78675d/content/test/BUILD.gn