Use webrtc::DesktopCapturer for screen capturer implementation.

media/video/capture/screen/screen_capture_frame_queue.h

Index: media/video/capture/screen/screen_capture_frame_queue.h
diff --git a/media/video/capture/screen/screen_capture_frame_queue.h b/media/video/capture/screen/screen_capture_frame_queue.h
index d36f15a462501a2b7b403015e8ee3ac2ed5b6c50..7d92024583f5f8ee45a0725f8af4f920a16fc1f6 100644
--- a/media/video/capture/screen/screen_capture_frame_queue.h
+++ b/media/video/capture/screen/screen_capture_frame_queue.h
@@ -8,14 +8,16 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 
-namespace media {
+namespace webrtc {
+class DesktopFrame;
+}  // namespace webrtc
 
-class ScreenCaptureFrame;
+namespace media {
 
 // Represents a queue of reusable video frames. Provides access to the 'current'
 // frame - the frame that the caller is working with at the moment, and to
 // the 'previous' frame - the predecessor of the current frame swapped by
-// DoneWithCurrentFrame() call, if any.
+// MoveToNextFrame() call, if any.

[Wez, 2013/04/26 18:48:14]

EmitCurrentFrameAndMoveToNext()?

[alexeypa (please no reviews), 2013/04/26 21:33:58]

nit: it is EmitCurrentFrameAndMoveToNext() in the code below.

[Sergey Ulanov, 2013/05/07 22:25:50]

Done.

[Sergey Ulanov, 2013/05/07 22:25:50]

Done.

 //
 // The caller is expected to (re)allocate frames if current_frame_needs_update()
 // is set. The caller can mark all frames in the queue for reallocation (when,
@@ -28,38 +30,44 @@ class ScreenCaptureFrameQueue {
 
   // Moves to the next frame in the queue, moving the 'current' frame to become
   // the 'previous' one.
-  void DoneWithCurrentFrame();
+  webrtc::DesktopFrame* EmitCurrentFrameAndMoveToNext();

[Wez, 2013/04/26 18:48:14]

Why not call this MoveToNextFrame() and document that it returns the
previously-current frame?

[Wez, 2013/04/26 18:48:14]

CLarify the ownership of the returned frame, for this call, and for the getters
below.

[Wez, 2013/04/26 18:48:14]

Also, for calls that return something and transfer ownership, prefer TakeFoo() -
EmitStuff() implies that the thing will be actively passed on e.g. to a callback
API, rather than passively returned to the caller, if you see what I mean?

[Sergey Ulanov, 2013/05/07 22:25:50]

Done.

[Sergey Ulanov, 2013/05/07 22:25:50]

MoveToNextFrame() is not verbose enough.

[Sergey Ulanov, 2013/05/07 22:25:50]

Right, but the frame is actually "emitted" by the capturer when it calls the
callback, that's why it's called EmittedFrame, so using "take" here would make
"EmittedFrame" more confusing.

 
   // Replaces the current frame with a new one allocated by the caller.
   // The existing frame (if any) is destroyed.
-  void ReplaceCurrentFrame(scoped_ptr<ScreenCaptureFrame> frame);
+  void ReplaceCurrentFrame(scoped_ptr<webrtc::DesktopFrame> frame);
 
   // Marks all frames obsolete and resets the previous frame pointer. No
   // frames are freed though as the caller can still access them.
   void SetAllFramesNeedUpdate();
 
-  ScreenCaptureFrame* current_frame() const {
-    return frames_[current_].get();
+  webrtc::DesktopFrame* current_frame() const {
+    return frames_[current_];
   }
 
   bool current_frame_needs_update() const {

[Wez, 2013/04/26 18:48:14]

You don't need this any more; just delete the frame rather than re-storing it in
ReturnEmittedFrame(), if it's marked needs_update_.

[Sergey Ulanov, 2013/05/07 22:25:50]

Yes, thanks!

     return !current_frame() || needs_update_[current_];
   }
 
-  ScreenCaptureFrame* previous_frame() const { return previous_; }
+  webrtc::DesktopFrame* previous_frame() const { return previous_; }
 
  private:
+  class EmittedFrame;
+  friend class EmittedFrame;
+
+  void ReturnEmittedFrame(webrtc::DesktopFrame* frame);

[Wez, 2013/04/26 18:48:14]

nit: Please document what this is for.

[Sergey Ulanov, 2013/05/07 22:25:50]

Done.

+
   // Index of the current frame.
   int current_;
 
   static const int kQueueLength = 2;
-  scoped_ptr<ScreenCaptureFrame> frames_[kQueueLength];
+  webrtc::DesktopFrame* frames_[kQueueLength];
+  EmittedFrame* emitted_frames_[kQueueLength];
 
   // True if the corresponding frame needs to be re-allocated.
   bool needs_update_[kQueueLength];
 
   // Points to the previous frame if any.
-  ScreenCaptureFrame* previous_;
+  webrtc::DesktopFrame* previous_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenCaptureFrameQueue);
 };