Make the video layer contents visible in OverlayFullscreenVideo mode

content/renderer/media/android/webmediaplayer_android.h

Index: content/renderer/media/android/webmediaplayer_android.h
diff --git a/content/renderer/media/android/webmediaplayer_android.h b/content/renderer/media/android/webmediaplayer_android.h
index 75dd1bec79cfd2a9e5605966474f18574f9a0390..6f407c8c2844dd345fc0a50ca23e9ef8f27817ad 100644
--- a/content/renderer/media/android/webmediaplayer_android.h
+++ b/content/renderer/media/android/webmediaplayer_android.h
@@ -347,6 +347,9 @@ class WebMediaPlayerAndroid
   scoped_refptr<media::VideoFrame> current_frame_;
   base::Lock current_frame_lock_;
 
+  // A lazily created transparent video frame to be displayed in fullscreen.
+  scoped_refptr<media::VideoFrame> fullscreen_frame_;

[qinmin, 2016/04/21 16:33:11]

why cannot we just use current_frame_?

[watk, 2016/04/21 18:56:28]

Well, it's a strange case. VideoResourceUpdater, which is used by the
compositor, asserts that each new VideoFrame it see have unique timestamps in
debug mode.. So that was DCHECKing when I created a new fullscreen frame each
time because they all had timestamp 0. So we could either:

a) change VideoResourceUpdater to not require that. Larger change and not clear
how to keep the useful behavior of catching bugs for normal playbacks where the
timestamps should be unique.
b) give fullscreen frames a dummy timestamp. Ugly and weird.
c) only ever create one fullscreen frame. Seemed like a reasonable thing to do
anyway as a micro optimization and it should use very 
little memory because it's a 1x1 image.

+
   base::ThreadChecker main_thread_checker_;
 
   // Message loop for media thread.