Don't histogram paint time after ending or seeking.

media/blink/webmediaplayer_impl.h

Index: media/blink/webmediaplayer_impl.h
diff --git a/media/blink/webmediaplayer_impl.h b/media/blink/webmediaplayer_impl.h
index 4726d393661f966f93097be588c2708bbb9f301c..1766d8c406ace9dc9a5e93fa62d5d7222558bd8f 100644
--- a/media/blink/webmediaplayer_impl.h
+++ b/media/blink/webmediaplayer_impl.h
@@ -712,6 +712,8 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   gfx::Size last_uploaded_frame_size_;
   base::TimeDelta last_uploaded_frame_timestamp_;
 
+  base::CancelableCallback<void(base::TimeTicks)> frame_time_report_cb_;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };