Make ThumbnailGenerator::AskForSnapshot support high DPI.

chrome/browser/tab_contents/thumbnail_generator.cc

 // 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.
 
 #include "chrome/browser/tab_contents/thumbnail_generator.h"
 
 #include <algorithm>
 #include <map>
 
 #include "base/bind.h"
@@ skipping 10 matching lines @@
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
 #include "googleurl/src/gurl.h"
 #include "skia/ext/image_operations.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/skia/include/core/SkBitmap.h"
+#include "ui/base/layout.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/scrollbar_size.h"
 #include "ui/gfx/skbitmap_operations.h"
 
 #if defined(OS_WIN)
 #include "base/win/windows_version.h"
 #endif
 
 // Overview
@@ skipping 222 matching lines @@
 }
 
 void ThumbnailGenerator::AskForSnapshot(RenderWidgetHost* renderer,
                                         const ThumbnailReadyCallback& callback,
                                         gfx::Size page_size,
                                         gfx::Size desired_size) {
   // We are going to render the thumbnail asynchronously now, so keep
   // this callback for later lookup when the rendering is done.
   static int sequence_num = 0;
   sequence_num++;
+  float scale_factor = ui::GetScaleFactorScale(ui::GetScaleFactorForNativeView(
+      renderer->GetView()->GetNativeView()));
+  gfx::Size desired_size_in_pixel = desired_size.Scale(scale_factor);
   scoped_ptr<TransportDIB> thumbnail_dib(TransportDIB::Create(
-      desired_size.width() * desired_size.height() * 4, sequence_num));
+      desired_size_in_pixel.GetArea() * 4, sequence_num));
 
 #if defined(USE_X11)
   // TODO: IPC a handle to the renderer like Windows.
   // http://code.google.com/p/chromium/issues/detail?id=89777
   NOTIMPLEMENTED();
   return;
 #else
 
 #if defined(OS_WIN)
   // Duplicate the handle to the DIB here because the renderer process does not
@@ skipping 308 matching lines @@
 void ThumbnailGenerator::DidStartLoading(
     content::RenderViewHost* render_view_host) {
   load_interrupted_ = false;
 }
 
 void ThumbnailGenerator::StopNavigation() {
   // This function gets called when the page loading is interrupted by the
   // stop button.
   load_interrupted_ = true;
 }