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

content/public/common/feature_h264_with_openh264_ffmpeg.cc

Index: content/public/common/feature_h264_with_openh264_ffmpeg.cc
diff --git a/content/public/common/feature_h264_with_openh264_ffmpeg.cc b/content/public/common/feature_h264_with_openh264_ffmpeg.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b13cfdfbf4b6296cfad83770bb70f6478593113c
--- /dev/null
+++ b/content/public/common/feature_h264_with_openh264_ffmpeg.cc
@@ -0,0 +1,17 @@
+// Copyright 2013 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.
+
+#include "content/public/common/feature_h264_with_openh264_ffmpeg.h"
+
+namespace content {
+
+#if BUILDFLAG(RTC_USE_H264)
+
+const base::Feature kWebRtcH264WithOpenH264FFmpeg {
+  "WebRTC-H264WithOpenH264FFmpeg", base::FEATURE_DISABLED_BY_DEFAULT
+};
+
+#endif  // BUILDFLAG(RTC_USE_H264)
+
+} // namespace content