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

content/public/renderer/media/webrtc/BUILD.gn

Index: content/public/renderer/media/webrtc/BUILD.gn
diff --git a/content/public/renderer/media/webrtc/BUILD.gn b/content/public/renderer/media/webrtc/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..cbad800e459918adc4a746cd93e88be710b3d2cd
--- /dev/null
+++ b/content/public/renderer/media/webrtc/BUILD.gn
@@ -0,0 +1,13 @@
+# Copyright 2016 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.
+
+source_set("finch_h264_with_openh264_ffmpeg") {
+  deps = [
+    "//content/public/renderer:renderer_features",
+  ]
+  sources = [
+    "finch_h264_with_openh264_ffmpeg.cc",
+    "finch_h264_with_openh264_ffmpeg.h",
+  ]
+}