Reason for revert:
Trybots red? Don't have time to intvestigate
Original issue's description:
> Default build flag |rtc_use_h264| to |proprietary_codecs|
> if not on Android/iOS.
>
> This means proprietary_codecs=1 && ffmpeg_branding=Chrome
> can be used to enable this H.264 enc/dec implementation
> instead of rtc_use_h264=1 && ffmpeg_branding=Chrome.
> This is used by both Chromium trybots (but not default
> Chromium build) and offical Chrome build, meaning we will
> be able to test and enable H.264 in chromium.
>
> This change would otherwise be enough to launch this
> feature in Chrome, but because we do not want to do that
> before we have chromium browser tests and are ready to flip
> the switch, this CL prevents chromium from using H.264 just
> yet: https://codereview.chromium.org/1641163002/ (landing
> this after that CL).
>
> BUG=chromium:500605, chromium:468365
>
> Committed: https://crrev.com/7cd94f66ebfe5bf808d7dcb8da069d35f4a2b31a
> Cr-Commit-Position: refs/heads/master@{#11506}
TBR=kjellander@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:500605, chromium:468365
Review URL: https://codereview.webrtc.org/1677623002
Cr-Commit-Position: refs/heads/master@{#11508}
c09525a547