WebRTC: Enable OpenH264 for WebRTC standalone bots.

scripts/slave/recipe_modules/chromium/config.py

Index: scripts/slave/recipe_modules/chromium/config.py
diff --git a/scripts/slave/recipe_modules/chromium/config.py b/scripts/slave/recipe_modules/chromium/config.py
index d467955af49d20f4a69d565d8d0e04789076dd33..1fb22f6258942b31b70770e7ee0fa45ebd98eb19 100644
--- a/scripts/slave/recipe_modules/chromium/config.py
+++ b/scripts/slave/recipe_modules/chromium/config.py
@@ -366,6 +366,12 @@ def proprietary_codecs(c, invert=False):
   c.gyp_env.GYP_DEFINES['proprietary_codecs'] = int(not invert)
 
 @config_ctx()
+def openh264(c):

[hbos_chromium, 2016/01/11 14:21:09]

Hmm the name "openh264" might be misleading here since this h264 feature relies
on both openh264 and ffmpeg. That's why I refer to it as "third_party_h264"
(perhaps not the best name either) since it relies on multiple third_party
libraries.

(I didn't simply call it webrtc_h264 because there is an iOS enc/dec too with
video toolbox. And HW versions as well for android. And plans for more. Ugh.)

[kjellander_chromium, 2016/01/12 10:11:45]

Well, OpenH264 is not used at all in Chromium, as the ffmpeg version implements
its own H264 decoder.
That makes me think this name is better than third_party_h264. Possibly
third_party_openh264 could be an option, but since there's no other openh264
anywhere, I think the third_party prefix doesn't add anything useful.
The naming of these configs also aren't that important, since they're only
referenced by the buildbot configurations.

+  ffmpeg_branding(c, branding='Chrome')

[hbos_chromium, 2016/01/11 14:21:09]

(Any idea what happens if multiple defs are used and ffmpeg_branding is
accidentally set multiple times? Just wondering since I see ffmpeg_branding in
other places in this file.)

[kjellander_chromium, 2016/01/12 10:11:45]

Any latter will overwrite the previous, but it's unlikely to happen since there
aren't that long chains that uses this setting. The resulting GYP_DEFINES will
also show up in the JSON files for the different bot configurations, allowing
reviewers to spot such an error.

+  c.gyp_env.GYP_DEFINES['use_openh264'] = 1
+  c.gyp_env.GYP_DEFINES['use_third_party_h264'] = 1
+
+@config_ctx()
 def chrome_with_codecs(c):
   ffmpeg_branding(c, branding='Chrome')
   proprietary_codecs(c)