Enable H.264 video WebRTC behind run-time flag and add WebRtcBrowserTest for H.264

Re-upload of https://codereview.chromium.org/1718883002/
but using #defines instead of BUILDFLAG to avoid problem
with generated header file described in comment #10:
https://codereview.chromium.org/1718883002/#msg10.
- This is Plan B.

Enable H.264 video WebRTC behind run-time flag and add
WebRtcBrowserTest for H.264.

The compile flag |rtc_use_h264| defaults to
|proprietary_codecs| which is used on some Chromium bots
and in the official Chrome build. The new run-time flag
|kWebRtcH264WithOpenH264FFmpeg| determines if the
|rtc_use_h264| encoder/decoder will be used at runtime.

The run-time flag is off by default.

This CL:
- Adds run-time flag and a new build target for it. It is
placed in content/public/common/ because it
can't/shouldn't be placed in the webrtc repo and
peer_connection_dependency_factory.cc lives in
content/renderer/media/webrtc/.
- Removed common_features (previously renderer_features)
and replaced its BUILDFLAG stuff with a #defines macro.
- Based on the run-time flag, enables or disables H.264
in peer_connection_dependency_factory.cc.
- If flag is on, runs a new H.264 browser test.

BUG=chromium:500605, chromium:468365

[hbos_chromium, 2016-02-23 08:31:28]

Description was changed from

==========
Re-upload of https://codereview.chromium.org/1718883002/
but using #defines instead of BUILDFLAG to avoid problem
with generated header file described in comment #10:
https://codereview.chromium.org/1718883002/#msg10

Enable H.264 video WebRTC behind run-time flag and add
WebRtcBrowserTest for H.264.

The compile flag |rtc_use_h264| defaults to
|proprietary_codecs| which is used on some Chromium bots
and in the official Chrome build. The new run-time flag
|kWebRtcH264WithOpenH264FFmpeg| determines if the
|rtc_use_h264| encoder/decoder will be used at runtime.

The run-time flag is off by default.

This CL:
- Adds run-time flag and a new build target for it. It is
placed in content/public/common/ because it
can't/shouldn't be placed in the webrtc repo and
peer_connection_dependency_factory.cc lives in
content/renderer/media/webrtc/.
- Removed common_features (previously renderer_features)
and replaced its BUILDFLAG stuff with a #defines macro.
- Based on the run-time flag, enables or disables H.264
in peer_connection_dependency_factory.cc.
- If flag is on, runs a new H.264 browser test.

BUG=chromium:500605, chromium:468365
==========

to

==========
Re-upload of https://codereview.chromium.org/1718883002/
but using #defines instead of BUILDFLAG to avoid problem
with generated header file described in comment #10:
https://codereview.chromium.org/1718883002/#msg10

Enable H.264 video WebRTC behind run-time flag and add
WebRtcBrowserTest for H.264.

The compile flag |rtc_use_h264| defaults to
|proprietary_codecs| which is used on some Chromium bots
and in the official Chrome build. The new run-time flag
|kWebRtcH264WithOpenH264FFmpeg| determines if the
|rtc_use_h264| encoder/decoder will be used at runtime.

The run-time flag is off by default.

This CL:
- Adds run-time flag and a new build target for it. It is
placed in content/public/common/ because it
can't/shouldn't be placed in the webrtc repo and
peer_connection_dependency_factory.cc lives in
content/renderer/media/webrtc/.
- Removed common_features (previously renderer_features)
and replaced its BUILDFLAG stuff with a #defines macro.
- Based on the run-time flag, enables or disables H.264
in peer_connection_dependency_factory.cc.
- If flag is on, runs a new H.264 browser test.

BUG=chromium:500605, chromium:468365
==========

[hbos_chromium, 2016-02-23 09:02:27]

Description was changed from

==========
Re-upload of https://codereview.chromium.org/1718883002/
but using #defines instead of BUILDFLAG to avoid problem
with generated header file described in comment #10:
https://codereview.chromium.org/1718883002/#msg10

Enable H.264 video WebRTC behind run-time flag and add
WebRtcBrowserTest for H.264.

The compile flag |rtc_use_h264| defaults to
|proprietary_codecs| which is used on some Chromium bots
and in the official Chrome build. The new run-time flag
|kWebRtcH264WithOpenH264FFmpeg| determines if the
|rtc_use_h264| encoder/decoder will be used at runtime.

The run-time flag is off by default.

This CL:
- Adds run-time flag and a new build target for it. It is
placed in content/public/common/ because it
can't/shouldn't be placed in the webrtc repo and
peer_connection_dependency_factory.cc lives in
content/renderer/media/webrtc/.
- Removed common_features (previously renderer_features)
and replaced its BUILDFLAG stuff with a #defines macro.
- Based on the run-time flag, enables or disables H.264
in peer_connection_dependency_factory.cc.
- If flag is on, runs a new H.264 browser test.

BUG=chromium:500605, chromium:468365
==========

to

==========
Re-upload of https://codereview.chromium.org/1718883002/
but using #defines instead of BUILDFLAG to avoid problem
with generated header file described in comment #10:
https://codereview.chromium.org/1718883002/#msg10.
- This is Plan B.

Enable H.264 video WebRTC behind run-time flag and add
WebRtcBrowserTest for H.264.

The compile flag |rtc_use_h264| defaults to
|proprietary_codecs| which is used on some Chromium bots
and in the official Chrome build. The new run-time flag
|kWebRtcH264WithOpenH264FFmpeg| determines if the
|rtc_use_h264| encoder/decoder will be used at runtime.

The run-time flag is off by default.

This CL:
- Adds run-time flag and a new build target for it. It is
placed in content/public/common/ because it
can't/shouldn't be placed in the webrtc repo and
peer_connection_dependency_factory.cc lives in
content/renderer/media/webrtc/.
- Removed common_features (previously renderer_features)
and replaced its BUILDFLAG stuff with a #defines macro.
- Based on the run-time flag, enables or disables H.264
in peer_connection_dependency_factory.cc.
- If flag is on, runs a new H.264 browser test.

BUG=chromium:500605, chromium:468365
==========

[hbos_chromium, 2016-02-23 11:37:28]

Patchset #2 (id:20001) has been deleted

[hbos_chromium, 2016-02-23 11:45:21]

https://codereview.chromium.org/1728453002/diff/1/content/content.gyp
File content/content.gyp (right):

https://codereview.chromium.org/1728453002/diff/1/content/content.gyp#newcode281
content/content.gyp:281: 'common_features',
The corresponding define is pulled in from content_renderer.gypi.

https://codereview.chromium.org/1728453002/diff/1/content/content.gyp#newcode322
content/content.gyp:322: 'common_features',
Same here.

[hbos_chromium, 2016-02-26 08:27:45]

"Plan A" CL (https://codereview.chromium.org/1718883002/) landed without getting
reverted, closing this one.