Mac Overlays: Add GPU back-pressure

ui/gl/gl_image_io_surface.h

 // Copyright 2013 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 UI_GL_GL_IMAGE_IO_SURFACE_H_
 #define UI_GL_GL_IMAGE_IO_SURFACE_H_
 
 #include <IOSurface/IOSurface.h>
 
 #include "base/mac/scoped_cftyperef.h"
@@ skipping 27 matching lines @@
   void WillUseTexImage() override {}
   void DidUseTexImage() override {}
   void WillModifyTexImage() override {}
   void DidModifyTexImage() override {}
   bool ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                             int z_order,
                             OverlayTransform transform,
                             const Rect& bounds_rect,
                             const RectF& crop_rect) override;
 
+  base::ScopedCFTypeRef<IOSurfaceRef> io_surface();
+
   static void SetLayerForWidget(gfx::AcceleratedWidget widget,
                                 CALayer* layer);
 
  protected:
   ~GLImageIOSurface() override;
 
  private:
   const gfx::Size size_;
   const unsigned internalformat_;
   BufferFormat format_;
   base::ScopedCFTypeRef<IOSurfaceRef> io_surface_;
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(GLImageIOSurface);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_IMAGE_IO_SURFACE_H_