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..c51c563f5bff67e25818ee52488c531e434ccda7 100644
--- a/media/video/capture/screen/screen_capture_frame_queue.h
+++ b/media/video/capture/screen/screen_capture_frame_queue.h
@@ -7,20 +7,27 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
+#include "media/video/capture/screen/shared_desktop_frame.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.
+// 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
+// MoveToNextFrame() call, if any.
 //
-// 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,
-// say, frame dimensions  change). The queue records which frames need updating
+// The caller is expected to (re)allocate frames if current_frame() returns
+// NULL. The caller can mark all frames in the queue for reallocation (when,
+// say, frame dimensions change). The queue records which frames need updating
 // which the caller can query.
+//
+// Frame consumer is expected to never hold more than kQueueLength frames
+// created by this function and it should release the earliest one before trying
+// to capture a new frame (i.e. before MoveToNextFrame() is called).
 class ScreenCaptureFrameQueue {
  public:
   ScreenCaptureFrameQueue();
@@ -28,38 +35,30 @@ class ScreenCaptureFrameQueue {
 
   // Moves to the next frame in the queue, moving the 'current' frame to become
   // the 'previous' one.
-  void DoneWithCurrentFrame();
+  void MoveToNextFrame();
 
   // 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();
+  void Reset();
 
-  ScreenCaptureFrame* current_frame() const {
+  SharedDesktopFrame* current_frame() const {
     return frames_[current_].get();
   }
 
-  bool current_frame_needs_update() const {
-    return !current_frame() || needs_update_[current_];
+  SharedDesktopFrame* previous_frame() const {
+    return frames_[(current_ + kQueueLength - 1) % kQueueLength].get();
   }
 
-  ScreenCaptureFrame* previous_frame() const { return previous_; }
-
  private:
   // Index of the current frame.
   int current_;
 
   static const int kQueueLength = 2;
-  scoped_ptr<ScreenCaptureFrame> 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_;
+  scoped_ptr<SharedDesktopFrame> frames_[kQueueLength];
 
   DISALLOW_COPY_AND_ASSIGN(ScreenCaptureFrameQueue);
 };