Adds kind-of-live thumbnail generation for a potential tab switcher.

chrome/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2006-2008 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/renderer_host/render_widget_host_view_mac.h"
 
 #include "base/histogram.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/browser_trial.h"
 #include "chrome/browser/renderer_host/backing_store.h"
@@ skipping 279 matching lines @@
           [[cocoa_view_ window] mouseLocationOutsideOfEventStream];
       [tooltip_ showToolTipAtPoint:event_point
                         withString:tooltip_nsstring
                         overWindow:[cocoa_view_ window]];
     }
   }
 }
 
 BackingStore* RenderWidgetHostViewMac::AllocBackingStore(
     const gfx::Size& size) {
-  return new BackingStore(size);
+  return new BackingStore(render_widget_host_, size);
 }
 
 // Display a popup menu for WebKit using Cocoa widgets.
 void RenderWidgetHostViewMac::ShowPopupWithItems(
     gfx::Rect bounds,
     int item_height,
     int selected_item,
     const std::vector<WebMenuItem>& items) {
   NSRect view_rect = [cocoa_view_ bounds];
   NSRect parent_rect = [parent_view_ bounds];
@@ skipping 97 matching lines @@
   renderWidgetHostView_->render_widget_host_->WasResized();
 }
 
 - (void)drawRect:(NSRect)dirtyRect {
   DCHECK(renderWidgetHostView_->render_widget_host_->process()->channel());
   DCHECK(!renderWidgetHostView_->about_to_validate_and_paint_);
 
   renderWidgetHostView_->invalid_rect_ = dirtyRect;
   renderWidgetHostView_->about_to_validate_and_paint_ = true;
   BackingStore* backing_store =
-      renderWidgetHostView_->render_widget_host_->GetBackingStore();
+      renderWidgetHostView_->render_widget_host_->GetBackingStore(true);
   skia::PlatformCanvas* canvas = backing_store->canvas();
   renderWidgetHostView_->about_to_validate_and_paint_ = false;
   dirtyRect = renderWidgetHostView_->invalid_rect_;
 
   if (backing_store) {
     gfx::Rect damaged_rect([self NSRectToRect:dirtyRect]);
 
     gfx::Rect bitmap_rect(0, 0,
                           backing_store->size().width(),
                           backing_store->size().height());
@@ skipping 74 matching lines @@
 
   if (closeOnDeactivate_)
     renderWidgetHostView_->KillSelf();
 
   renderWidgetHostView_->render_widget_host_->Blur();
 
   return YES;
 }
 
 @end