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

content/renderer/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/features.gni")
 import("//build/config/ui.gni")
-import("//build/buildflag_header.gni")
 import("//content/renderer/renderer.gni")
 import("//media/media_options.gni")
-import("//third_party/webrtc/build/webrtc.gni")
 
 source_set("renderer") {
   # Only the public target should depend on this. All other targets (even
   # internal content ones) should depend on the public one.
   visibility = [ "//content/public/renderer:renderer_sources" ]
 
   sources = rebase_path(content_renderer_gypi_values.private_renderer_sources,
                         ".",
                         "//content")
 
   configs += [
     "//content:content_implementation",
     "//build/config/compiler:no_size_t_to_int_warning",
     "//content/public/common:mojo_shell_client",
   ]
   defines = []
 
   deps = [
-    ":renderer_features",
     "//base:i18n",
     "//cc",
     "//cc/blink",
     "//cc/proto",
     "//cc/surfaces",
     "//cc/surfaces:surface_id",
     "//components/scheduler:scheduler",
     "//components/url_formatter",
     "//components/webusb",
     "//content:resources",
     "//content/common:mojo_bindings",
     "//content/public/child:child_sources",
+    "//content/public/common:common_features",
     "//content/public/common:common_sources",
+    "//content/public/common:feature_h264_with_openh264_ffmpeg",
     "//content/public/common:mojo_bindings",
     "//crypto:platform",
     "//device/battery:mojo_bindings",
     "//device/bluetooth",
     "//device/usb/public/interfaces",
     "//device/vibration:mojo_bindings",
     "//gin",
     "//gpu",
     "//gpu/blink",
     "//gpu/command_buffer/client:gles2_interface",
@@ skipping 184 matching lines @@
   }
 
   if (use_seccomp_bpf) {
     defines += [ "USE_SECCOMP_BPF" ]
   }
 
   if (use_ozone) {
     deps += [ "//ui/ozone" ]
   }
 }
-
-buildflag_header("renderer_features") {
-  header = "renderer_features.h"
-
-  flags = [ "RTC_USE_H264=$rtc_use_h264" ]
-}