Mac ÜC: Enable GPU back-pressure from the browser to the renderer

content/browser/compositor/browser_compositor_view_mac.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_COMPOSITOR_BROWSER_COMPOSITOR_VIEW_MAC_H_
 #define CONTENT_BROWSER_COMPOSITOR_BROWSER_COMPOSITOR_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_nsobject.h"
 #include "cc/output/software_frame_data.h"
 #include "content/browser/renderer_host/compositing_iosurface_layer_mac.h"
 #include "content/browser/renderer_host/software_layer_mac.h"
 #include "skia/ext/platform_canvas.h"
 #include "ui/compositor/compositor.h"
 #include "ui/gfx/geometry/size.h"
 
-@class BrowserCompositorViewMac;
+namespace content {
+class BrowserCompositorViewMacHelper;
+
+class BrowserCompositorViewMacClient {
+ public:
+  virtual void BrowserCompositorDidDrawFrame() = 0;
+};
+
+}  // namespace content
 
 // Additions to the NSView interface for compositor frames.
 @interface NSView (BrowserCompositorView)
 - (void)gotAcceleratedIOSurfaceFrame:(uint64)surface_handle
                        withPixelSize:(gfx::Size)pixel_size
                      withScaleFactor:(float)scale_factor;
 
 - (void)gotSoftwareFrame:(cc::SoftwareFrameData*)frame_data
          withScaleFactor:(float)scale_factor
               withCanvas:(SkCanvas*)canvas;
-@end
+@end  // NSView (BrowserCompositorView)
 
 // NSView drawn by a ui::Compositor. The superview of this view is responsible
 // for changing the ui::Compositor SizeAndScale and calling layoutLayers when
 // the size of the parent view may change. This interface is patterned after
 // the needs of RenderWidgetHostViewCocoa, and could change.
 @interface BrowserCompositorViewMac : NSView {
   scoped_ptr<ui::Compositor> compositor_;
+
   base::scoped_nsobject<CALayer> background_layer_;
   base::scoped_nsobject<CompositingIOSurfaceLayer> accelerated_layer_;
   base::scoped_nsobject<SoftwareLayer> software_layer_;
+
+  content::BrowserCompositorViewMacClient* client_;
+  scoped_ptr<content::BrowserCompositorViewMacHelper> helper_;
 }
 
 // Initialize to render the content of a specific superview.
-- (id)initWithSuperview:(NSView*)view;
+- (id)initWithSuperview:(NSView*)view
+             withClient:(content::BrowserCompositorViewMacClient*)client;
 
 // Re-position the layers to the correct place when this view's superview
 // changes size, or when the accelerated or software content changes.
 - (void)layoutLayers;
 
+// Disallow further access to the client.
+- (void)resetClient;
+
 // Access the underlying ui::Compositor for this view.
 - (ui::Compositor*)compositor;
-@end
+@end  // BrowserCompositorViewMac
 
 #endif  // CONTENT_BROWSER_COMPOSITOR_BROWSER_COMPOSITOR_VIEW_MAC_H_