Prevent browser thumbnailer from trying to read from frontbuffer (surface texture) when none exists.

content/browser/renderer_host/render_widget_host_view_win.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 "content/browser/renderer_host/render_widget_host_view_win.h"
 
 #include <algorithm>
 #include <peninputpanel_i.c>
 
 #include "base/bind.h"
@@ skipping 888 matching lines @@
 }
 
 void RenderWidgetHostViewWin::Blur() {
   NOTREACHED();
 }
 
 bool RenderWidgetHostViewWin::HasFocus() const {
   return ::GetFocus() == m_hWnd;
 }
 
+bool RenderWidgetHostViewWin::IsSurfaceAvailableForCopy() const {
+  return !!render_widget_host_->GetBackingStore(false) ||
+      !!accelerated_surface_.get();
+}
+
 void RenderWidgetHostViewWin::Show() {
   if (!is_fullscreen_) {
     DCHECK(parent_hwnd_);
     DCHECK(parent_hwnd_ != ui::GetWindowToParentTo(true));
     SetParent(parent_hwnd_);
   }
   ShowWindow(SW_SHOW);
 
   DidBecomeSelected();
 }
@@ skipping 2086 matching lines @@
 void RenderWidgetHostViewWin::ResetPointerDownContext() {
   // If the default focus on the page is on an edit field and we did not
   // receive a focus change in the context of a pointer down message, it means
   // that the pointer down message occurred on the edit field and we should
   // display the on screen keyboard
   if (!received_focus_change_after_pointer_down_ && virtual_keyboard_)
     DisplayOnScreenKeyboardIfNeeded();
   received_focus_change_after_pointer_down_ = false;
   pointer_down_context_ = false;
 }