mac: Improve framerate on accelerated pages in HiDPI mode.

content/browser/renderer_host/compositing_iosurface_mac.h

 // Copyright (c) 2012 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_RENDERER_HOST_ACCELERATED_COMPOSITING_VIEW_MAC_H
 #define CONTENT_BROWSER_RENDERER_HOST_ACCELERATED_COMPOSITING_VIEW_MAC_H
 
 #import <Cocoa/Cocoa.h>
 #include <QuartzCore/QuartzCore.h>
 
@@ skipping 36 matching lines @@
 
   // Disassociate the GL context with the NSView and unref the IOSurface. Do
   // this to switch to software drawing mode.
   void ClearDrawable();
 
   bool HasIOSurface() { return !!io_surface_.get(); }
 
   const gfx::Size& pixel_io_surface_size() const {
     return pixel_io_surface_size_;
   }
+  const gfx::Size& io_surface_size() const { return io_surface_size_; }

[jbates, 2012/06/12 17:11:13]

I think this should be renamed so that it's clear that it's not the pixel size.
Can it mention something about nsview coordinates? How about
nsview_io_surface_size() with a comment that it's the surface size mapped to
NSView coordinates.

 
   bool is_vsync_disabled() const { return is_vsync_disabled_; }
 
  private:
   // Vertex structure for use in glDraw calls.
   struct SurfaceVertex {
     SurfaceVertex() : x_(0.0f), y_(0.0f), tx_(0.0f), ty_(0.0f) { }
     // Currently the texture coords are always the same as vertex coords.
     void set(float x, float y, float tx, float ty) {
       x_ = x;
@@ skipping 54 matching lines @@
 
   // GL context
   scoped_nsobject<NSOpenGLContext> glContext_;
   CGLContextObj cglContext_;  // weak, backed by |glContext_|.
 
   // IOSurface data.
   uint64 io_surface_handle_;
   base::mac::ScopedCFTypeRef<CFTypeRef> io_surface_;
 
   // The width and height of the io surface.
-  gfx::Size pixel_io_surface_size_;
+  gfx::Size pixel_io_surface_size_;  // In pixels.
+  gfx::Size io_surface_size_;  // In view units.
 
   // The "live" OpenGL texture referring to this IOSurfaceRef. Note
   // that per the CGLTexImageIOSurface2D API we do not need to
   // explicitly update this texture's contents once created. All we
   // need to do is ensure it is re-bound before attempting to draw
   // with it.
   GLuint texture_;
 
   // Shader parameters.
   GLuint shader_program_blit_rgb_;
   GLint blit_rgb_sampler_location_;
   GLuint shader_program_white_;
 
   SurfaceQuad quad_;
 
   bool is_vsync_disabled_;
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_ACCELERATED_COMPOSITING_VIEW_MAC_H