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

content/content.gyp

Index: content/content.gyp
diff --git a/content/content.gyp b/content/content.gyp
index 232814f69f63304ed9372438ad6d8f32cefe7d04..298885a8e2c8c45911bfb69ef1540d60c94a8ad3 100644
--- a/content/content.gyp
+++ b/content/content.gyp
@@ -23,27 +23,24 @@
   },
   'targets': [
     {
-      # GN version: //content/renderer:renderer_features
-      'target_name': 'renderer_features',
+      # GN version: //content/public/common:feature_h264_with_openh264_ffmpeg
+      'target_name': 'feature_h264_with_openh264_ffmpeg',
+      'type': 'static_library',
+      'include_dirs': [ '<@(DEPTH)' ],
       'includes': [
-        '../build/buildflag_header.gypi',
         '../third_party/webrtc/build/common.gypi',
       ],
       'conditions': [
-        # This conditional looks insane, but without it |rtc_use_h264| is not
-        # recognized as defined. Might have something to do with scopes. Moving
-        # the inclusion of third_party/webrtc/build/common.gypi to outside of
-        # 'targets' is not an option, then we get compile errors.
-        # TODO(hbos): crbug.com/584219
-        ['1==1', {
-          'variables': {
-            'buildflag_header_path': 'content/renderer/renderer_features.h',
-            'buildflag_flags': [
-              'RTC_USE_H264=<(rtc_use_h264)',
-            ],
-          },
+        ['rtc_use_h264==1', {
+          'defines': [
+            'BUILDFLAG_RTC_USE_H264',
+          ],
         }],
       ],
+      'sources': [
+        'public/common/feature_h264_with_openh264_ffmpeg.cc',
+        'public/common/feature_h264_with_openh264_ffmpeg.h',
+      ],
     },
   ],
   'includes': [
@@ -268,7 +265,6 @@
             'content_child',
             'content_common',
             'content_resources',
-            'renderer_features',
           ],
           'export_dependent_settings': [
             'content_common',
@@ -307,7 +303,6 @@
           'dependencies': [
             '../third_party/webrtc/modules/modules.gyp:webrtc_h264',
             'content_resources',
-            'renderer_features',
           ],
           'conditions': [
             ['chromium_enable_vtune_jit_for_v8==1', {