Add histogram for percentage of sent frames that are limited in resolution due to bandwidth.

webrtc/video_frame.h

Index: webrtc/video_frame.h
diff --git a/webrtc/video_frame.h b/webrtc/video_frame.h
index d70a746daeb49334193c99d522cefd275615981c..abfd7311ef5d8f72891ee9d14f1f7fe128a0967e 100644
--- a/webrtc/video_frame.h
+++ b/webrtc/video_frame.h
@@ -181,6 +181,16 @@ class EncodedImage {
   EncodedImage(uint8_t* buffer, size_t length, size_t size)
       : _buffer(buffer), _length(length), _size(size) {}
 
+  struct AdaptReason {
+    AdaptReason()
+        : bw_limited_resolution_available(false),
+          bw_limited_resolution(false) {}
+
+    bool bw_limited_resolution_available;  // True if |bw_limited_resolution|
+                                           // is provided.
+    bool bw_limited_resolution;  // True if higher resolutions of this frame are
+                                 // not sent due to bandwidth.
+  };
   uint32_t _encodedWidth = 0;
   uint32_t _encodedHeight = 0;
   uint32_t _timeStamp = 0;
@@ -193,6 +203,7 @@ class EncodedImage {
   size_t _length;
   size_t _size;
   bool _completeFrame = false;
+  AdaptReason adapt_reason_;
 };
 
 }  // namespace webrtc