rtc_use_h264 flag for building OpenH264/FFmpeg

webrtc/build/common.gypi

Index: webrtc/build/common.gypi
diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index 14f7e9a4a368ba300dc56e0d7f5bbad9617ac0ae..d483f24a53d952749fb0b2a9965471af046ee555 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -137,16 +137,14 @@
     # Enabling this may break interop with Android clients that support H264.
     'use_objc_h264%': 0,
 
-    # Enable this to build H.264 encoder/decoder using third party libraries.
-    # Encoding uses OpenH264 and decoding uses FFmpeg. Because of this, OpenH264
-    # and FFmpeg have to be correctly enabled separately.
-    # - use_openh264=1 is required for OpenH264 targets to be defined.
-    # - ffmpeg_branding=Chrome is one way to support H.264 decoding in FFmpeg.
-    #   FFmpeg can be built with/without H.264 support, see 'ffmpeg_branding'.
-    #   Without it, it compiles but H264DecoderImpl fails to initialize.
+    # Enable this to build OpenH264 encoder/FFmpeg decoder. This is supported on
+    # all platforms except iOS. Because FFmpeg can be built with/without H.264
+    # support, |ffmpeg_branding| has to separately be set to a value that
+    # includes H.264, for example "Chrome". If FFmpeg is built without H.264,
+    # compilation succeeds but |H264DecoderImpl| fails to initialize.
     # CHECK THE OPENH264, FFMPEG AND H.264 LICENSES/PATENTS BEFORE BUILDING.
     # http://www.openh264.org, https://www.ffmpeg.org/
-    'use_third_party_h264%': 0,  # TODO(hbos): To be used in follow-up CL(s).
+    'rtc_use_h264%': 0,  # TODO(hbos): enc/dec in follow up CL(s).
 
     'conditions': [
       ['build_with_chromium==1', {