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

content/public/renderer/BUILD.gn

Index: content/public/renderer/BUILD.gn
diff --git a/content/public/renderer/BUILD.gn b/content/public/renderer/BUILD.gn
index 719eadf6771980e13dd3748f7c48c017414328ae..31ce5bbf16b0fd92c27c1c9767f89ca0100417a7 100644
--- a/content/public/renderer/BUILD.gn
+++ b/content/public/renderer/BUILD.gn
@@ -2,8 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/buildflag_header.gni")
 import("//build/config/features.gni")
 import("//content/renderer/renderer.gni")
+import("//third_party/webrtc/build/webrtc.gni")
 
 # See //content/BUILD.gn for how this works.
 group("renderer") {
@@ -18,6 +20,12 @@ group("renderer") {
   }
 }
 
+buildflag_header("renderer_features") {
+  header = "renderer_features.h"
+
+  flags = [ "RTC_USE_H264=$rtc_use_h264" ]
+}
+
 source_set("renderer_sources") {
   visibility = [ "//content/*" ]
 
@@ -49,7 +57,10 @@ source_set("renderer_sources") {
         rebase_path(content_renderer_gypi_values.public_renderer_webrtc_sources,
                     ".",
                     "//content")
-    deps += [ "//third_party/webrtc" ]
+    deps += [
+      "//content/public/renderer/media/webrtc:finch_h264_with_openh264_ffmpeg",
+      "//third_party/webrtc",
+    ]
   }
 
   if (enable_plugins) {