media: Refactor SkCanvasVideoRenderer to use SkImages and not SkBitmaps.

media/blink/skcanvas_video_renderer.h

Index: media/blink/skcanvas_video_renderer.h
diff --git a/media/blink/skcanvas_video_renderer.h b/media/blink/skcanvas_video_renderer.h
index 9b75cd01e0fad04c242dd1463c73c6142e853845..94a6fa71697ed0e73e9135643e8863e94fc492e3 100644
--- a/media/blink/skcanvas_video_renderer.h
+++ b/media/blink/skcanvas_video_renderer.h
@@ -11,7 +11,6 @@
 #include "media/base/media_export.h"
 #include "media/base/video_rotation.h"
 #include "media/filters/context_3d.h"
-#include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/gfx/geometry/rect.h"
 
@@ -20,7 +19,6 @@ class SkCanvas;
 namespace media {
 
 class VideoFrame;
-class VideoImageGenerator;
 
 // Handles rendering of VideoFrames to SkCanvases, doing any necessary YUV
 // conversion and caching of resulting RGB bitmaps.
@@ -70,25 +68,6 @@ class MEDIA_EXPORT SkCanvasVideoRenderer {
                                                bool flip_y);
 
  private:
-  void ResetLastFrame();
-  void ResetAcceleratedLastFrame();
-
-  // An RGB bitmap and corresponding timestamp of the previously converted
-  // video frame data by software color space conversion.
-  SkBitmap last_frame_;

[dshwang, 2015/05/28 15:54:18]

This cache optimization is gone.
Canvas2D and WebGL can draws same video frame multiple times. After this CL,
this class decodes the video frame or create the video texture every time.

[Daniele Castagna, 2015/05/28 22:48:12]

Skia caches the result internally. The VideoFrame is decoded (if by the coded
you mean YUV -> RGB when necessary) and then the RGBA cached inside Skia.
In addition to that, Skia uses discardable memory and has a budget that would
apply to this cache too. In this way we save memory when needed too.

The texture is not created everytime. Skia has a pool of textures.

-  base::TimeDelta last_frame_timestamp_;
-  // If |last_frame_| is not used for a while, it's deleted to save memory.
-  base::DelayTimer<SkCanvasVideoRenderer> frame_deleting_timer_;
-
-  // This is a hardware accelerated copy of the frame generated by
-  // |accelerated_generator_|.
-  // It's used when |canvas| parameter in Paint() is Ganesh canvas.
-  // Note: all GrContext in SkCanvas instances are same.
-  SkBitmap accelerated_last_frame_;

[dshwang, 2015/05/28 15:54:18]

software canvas and accelerated canvas draws the same video frame multiple
times. It's why software caches and gpu caches are kept separately.

for example, ./blink/tools/run_layout_tests.py
virtual/gpu/fast/canvas/yuv-video-on-accelerated-canvas.html

After this CL, same SkImage deals with both software SkCanvas and ganesh
SkCanvas. I'm not sure if it's ok.

[Daniele Castagna, 2015/05/28 22:48:12]

I don't know too much about the internal of Skia, but I don't see why they
couldn't cache both in the software and gpu case.
That's not the case. We create a new SkImage every time. Skia internally could
cache the two separately.

-  VideoImageGenerator* accelerated_generator_;
-  base::TimeDelta accelerated_last_frame_timestamp_;
-  base::DelayTimer<SkCanvasVideoRenderer> accelerated_frame_deleting_timer_;
-
   DISALLOW_COPY_AND_ASSIGN(SkCanvasVideoRenderer);
 };