Support browser side thumbnailing for GPU composited pages on Windows.

content/public/browser/render_widget_host.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_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_
 #define CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_
 #pragma once
 
 #include "content/common/content_export.h"
 #include "content/public/browser/keyboard_listener.h"
@@ skipping 159 matching lines @@
   // succeeding UpdateTextDirection() requests until calling
   // NotifyTextDirection(). (We may receive keydown events even after we
   // canceled updating the text direction because of auto-repeat.)
   // Note: we cannot undo this change for compatibility with Firefox and IE.
   virtual void UpdateTextDirection(WebKit::WebTextDirection direction) = 0;
   virtual void NotifyTextDirection() = 0;
 
   virtual void Blur() = 0;
 
   // Copies the contents of the backing store into the given (uninitialized)
-  // PlatformCanvas. Returns true on success, false otherwise.
-  virtual bool CopyFromBackingStore(skia::PlatformCanvas* output) = 0;
+  // PlatformCanvas. Returns true on success, false otherwise. When accelerated
+  // compositing is active, the contents is copied from the compositing surface.
+  // If non empty |dest_size| is given, the content is shrinked so that it fits
+  // in |dest_size|. If |dest_size| is larger than the contens size, the
+  // content is not resized. If |dest_size| is empty, the original size of the
+  // contents is copied.
+  virtual bool CopyFromBackingStore(const gfx::Size& dest_size,

[jam, 2012/03/14 17:56:42]

you're not setting this anywhere now, so why are you adding it?

[mazda, 2012/03/14 18:19:05]

I'll set it soon in ThumbnailGenerator::GetBitmapForRenderWidgetHost after I
find out an optimal size with more experiments.

+                                    skia::PlatformCanvas* output) = 0;
 
 #if defined(TOOLKIT_GTK)
   // Paint the backing store into the target's |dest_rect|.
   virtual bool CopyFromBackingStoreToGtkWindow(const gfx::Rect& dest_rect,
                                                GdkWindow* target) = 0;
 #elif defined(OS_MACOSX)
   virtual gfx::Size GetBackingStoreSize() = 0;
   virtual bool CopyFromBackingStoreToCGContext(const CGRect& dest_rect,
                                                CGContextRef target) = 0;
 #endif
@@ skipping 88 matching lines @@
   // within content/.  This method is necessary because
   // RenderWidgetHost is the root of a diamond inheritance pattern, so
   // subclasses inherit it virtually, which removes our ability to
   // static_cast to the subclass.
   virtual RenderWidgetHostImpl* AsRenderWidgetHostImpl() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_