Add framerate to VideoSinkWants and ability to signal on overuse

webrtc/video_send_stream.h

Index: webrtc/video_send_stream.h
diff --git a/webrtc/video_send_stream.h b/webrtc/video_send_stream.h
index 680eb02bc46805ae701342faabd54a81d3581f87..beb34940fce5e5029fa83b568de785dba2c6a158 100644
--- a/webrtc/video_send_stream.h
+++ b/webrtc/video_send_stream.h
@@ -214,12 +214,15 @@ class VideoSendStream {
 
   // Based on the spec in
   // https://w3c.github.io/webrtc-pc/#idl-def-rtcdegradationpreference.
-  enum class DegradationPreference {
-    kMaintainResolution,
+  enum class DegradationPreference : size_t {
+    kMaintainResolution = 0,
     // TODO(perkj): Implement kMaintainFrameRate. kBalanced will drop frames
     // if the encoder overshoots or the encoder can not encode fast enough.
-    kBalanced,
+    kBalanced = 1,
   };
+  static const size_t kNumDegradationPreferences =
+      static_cast<size_t>(DegradationPreference::kBalanced) + 1;
+
   virtual void SetSource(
       rtc::VideoSourceInterface<webrtc::VideoFrame>* source,
       const DegradationPreference& degradation_preference) = 0;