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

content/public/common/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chromecast_build.gni")
 import("//build/config/features.gni")
 import("//content/common/common.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
+import("//third_party/webrtc/build/webrtc.gni")
 
 # See //content/BUILD.gn for how this works.
 group("common") {
   if (is_component_build) {
     public_deps = [
       "//content",
     ]
   } else {
     public_deps = [
       ":common_sources",
@@ skipping 93 matching lines @@
 }
 
 mojom("mojo_bindings") {
   sources = [
     "background_sync.mojom",
     "mojo_geoposition.mojom",
     "permission_status.mojom",
     "service_worker_event_status.mojom",
   ]
 }
+
+source_set("feature_h264_with_openh264_ffmpeg") {
+  if (rtc_use_h264) {
+    defines = [ "BUILDFLAG_RTC_USE_H264" ]
+  }
+  sources = [
+    "feature_h264_with_openh264_ffmpeg.cc",
+    "feature_h264_with_openh264_ffmpeg.h",
+  ]
+}