Make MediaCodecEncoder fallback to a software encoder on failure.

webrtc/video_encoder.h

Index: webrtc/video_encoder.h
diff --git a/webrtc/video_encoder.h b/webrtc/video_encoder.h
index 2584568533a21fda42aef162f670a26710fc64b5..88ede32131293680cd1bd00474904a4729d149ce 100644
--- a/webrtc/video_encoder.h
+++ b/webrtc/video_encoder.h
@@ -83,6 +83,9 @@ class VideoEncoder {
   };
 
   static VideoEncoder* Create(EncoderType codec_type);
+  // Returns true if this type of encoder can be created using
+  // VideoEncoder::Create.
+  static bool IsSupported(EncoderType codec_type);
 
   static VideoCodecVP8 GetDefaultVp8Settings();
   static VideoCodecVP9 GetDefaultVp9Settings();