clang/win: Let some chromium_code targets build with -Wextra.

content/browser/renderer_host/legacy_render_widget_host_win.cc

 // Copyright (c) 2014 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/legacy_render_widget_host_win.h"
 
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/win/windows_version.h"
 #include "content/browser/accessibility/browser_accessibility_manager_win.h"
@@ skipping 148 matching lines @@
   // because it sometimes gets sign-extended incorrectly (but not always).
   DWORD obj_id = static_cast<DWORD>(static_cast<DWORD_PTR>(l_param));
 
   if (kIdScreenReaderHoneyPot == obj_id) {
     // When an MSAA client has responded to our fake event on this id,
     // enable screen reader support.
     BrowserAccessibilityState::GetInstance()->OnScreenReaderDetected();
     return static_cast<LRESULT>(0L);
   }
 
-  if (OBJID_CLIENT != obj_id || !host_)
+  if (static_cast<DWORD>(OBJID_CLIENT) != obj_id || !host_)
     return static_cast<LRESULT>(0L);
 
   RenderWidgetHostImpl* rwhi = RenderWidgetHostImpl::From(
       host_->GetRenderWidgetHost());
   if (!rwhi)
     return static_cast<LRESULT>(0L);
 
   BrowserAccessibilityManagerWin* manager =
       static_cast<BrowserAccessibilityManagerWin*>(
           rwhi->GetRootBrowserAccessibilityManager());
@@ skipping 224 matching lines @@
       direct_manipulation_helper_->Activate(hwnd());
     } else if (window_pos->flags & SWP_HIDEWINDOW) {
       direct_manipulation_helper_->Deactivate(hwnd());
     }
   }
   SetMsgHandled(FALSE);
   return 0;
 }
 
 }  // namespace content