Set hbrBackground on wndclass, fixes white flash on resize

ui/base/win/window_impl.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 "ui/base/win/window_impl.h"
 
 #include <list>
 
 #include "base/debug/alias.h"
 #include "base/memory/singleton.h"
@@ skipping 82 matching lines @@
   for (RegisteredClasses::const_iterator i = registered_classes_.begin();
        i != registered_classes_.end(); ++i) {
     if (class_info.Equals(i->info))
       return i->atom;
   }
 
   // No class found, need to register one.
   string16 name = string16(WindowImpl::kBaseClassName) +
       base::IntToString16(registered_count_++);
 
-  HBRUSH background = NULL;
+  HBRUSH background = reinterpret_cast<HBRUSH>(COLOR_WINDOW);
   WNDCLASSEX window_class;
   base::win::InitializeWindowClass(
       name.c_str(),
       &base::win::WrappedWindowProc<WindowImpl::WndProc>,
       class_info.style,
       0,
       0,
       NULL,
       reinterpret_cast<HBRUSH>(background + 1),
       NULL,
@@ skipping 151 matching lines @@
   return window->OnWndProc(message, w_param, l_param);
 }
 
 ATOM WindowImpl::GetWindowClassAtom() {
   HICON icon = GetDefaultWindowIcon();
   ClassInfo class_info(initial_class_style(), icon);
   return ClassRegistrar::GetInstance()->RetrieveClassAtom(class_info);
 }
 
 }  // namespace ui