Adding third_party/openh264 build files for encoding

build/config/features.gni

Index: build/config/features.gni
diff --git a/build/config/features.gni b/build/config/features.gni
index 9fb4205257a30f640613ee21b27252fd030e7133..04c72fb562a4318ac884ab5bae4090ac85c51f59 100644
--- a/build/config/features.gni
+++ b/build/config/features.gni
@@ -54,6 +54,12 @@ declare_args() {
   # TODO(GYP) make mac work.
   enable_webrtc = !is_ios && !is_mac
 
+  # Enable this to build OpenH264.
+  # CHECK THE OPENH264 LICENSE BEFORE BUILDING. The default value should be
+  # false, the open source version of Chromium should not build this by default
+  # due to license and patent reasons.
+  use_openh264 = true
+
   # Enables the Media Router.
   enable_media_router = !is_ios