remoting: remove usage of CapturedFrame.elapsed_time in CastVideoCapturerAdapter

remoting/host/cast_video_capturer_adapter.h

Index: remoting/host/cast_video_capturer_adapter.h
diff --git a/remoting/host/cast_video_capturer_adapter.h b/remoting/host/cast_video_capturer_adapter.h
index 8a5db48f66df37a9108dbcd8ecd82418dd234651..88d47ff3821efd881c3df56839ce37070d3480d2 100644
--- a/remoting/host/cast_video_capturer_adapter.h
+++ b/remoting/host/cast_video_capturer_adapter.h
@@ -7,6 +7,7 @@
 
 #include <vector>
 
+#include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "base/timer/timer.h"
@@ -69,9 +70,6 @@ class CastVideoCapturerAdapter : public cricket::VideoCapturer,
   // Used to schedule periodic screen captures.
   scoped_ptr<base::RepeatingTimer> capture_timer_;
 
-  // Used to set the elapsed_time attribute of captured frames.
-  base::TimeTicks start_time_;
-
   DISALLOW_COPY_AND_ASSIGN(CastVideoCapturerAdapter);
 };