Measure encoding time on encode callbacks.

webrtc/frame_callback.h

Index: webrtc/frame_callback.h
diff --git a/webrtc/frame_callback.h b/webrtc/frame_callback.h
index b7f2210334d9870b0e7e64f7d0d61a7b8d3574e2..2bae25036d9aaa5da3d4845b9fd33103cab3ef15 100644
--- a/webrtc/frame_callback.h
+++ b/webrtc/frame_callback.h
@@ -12,6 +12,7 @@
 #define WEBRTC_FRAME_CALLBACK_H_
 
 #include <stddef.h>
+#include <stdint.h>
 
 #include "webrtc/common_types.h"
 
@@ -43,6 +44,7 @@ class I420FrameCallback {
 class EncodedFrameObserver {
  public:
   virtual void EncodedFrameCallback(const EncodedFrame& encoded_frame) = 0;
+  virtual void OnEncodeTiming(int64_t capture_ntp_ms, int encode_duration_ms) {}
 
  protected:
   virtual ~EncodedFrameObserver() {}