Merge 279172 "Proper fix for accessibility in Windows 64 build."

ui/views/win/hwnd_message_handler.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/views/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <oleacc.h>
 #include <shellapi.h>
 #include <wtsapi32.h>
@@ skipping 27 matching lines @@
 #include "ui/views/views_delegate.h"
 #include "ui/views/widget/monitor_win.h"
 #include "ui/views/widget/widget_hwnd_utils.h"
 #include "ui/views/win/fullscreen_handler.h"
 #include "ui/views/win/hwnd_message_handler_delegate.h"
 #include "ui/views/win/scoped_fullscreen_visibility.h"
 
 namespace views {
 namespace {
 
-// A version of the OBJID_CLIENT constant that works in 64-bit mode too.
-static const LPARAM kObjIdClient = static_cast<ULONG>(OBJID_CLIENT);
-
 // MoveLoopMouseWatcher is used to determine if the user canceled or completed a
 // move. win32 doesn't appear to offer a way to determine the result of a move,
 // so we install hooks to determine if we got a mouse up and assume the move
 // completed.
 class MoveLoopMouseWatcher {
  public:
   MoveLoopMouseWatcher(HWNDMessageHandler* host, bool hide_on_escape);
   ~MoveLoopMouseWatcher();
 
   // Returns true if the mouse is up, or if we couldn't install the hook.
@@ skipping 1351 matching lines @@
     minmax_info->ptMaxTrackSize.y = max_window_size.height();
   }
   SetMsgHandled(FALSE);
 }
 
 LRESULT HWNDMessageHandler::OnGetObject(UINT message,
                                         WPARAM w_param,
                                         LPARAM l_param) {
   LRESULT reference_result = static_cast<LRESULT>(0L);
 
+  // Only the lower 32 bits of l_param are valid when checking the object id
+  // because it sometimes gets sign-extended incorrectly (but not always).
+  DWORD obj_id = static_cast<DWORD>(static_cast<DWORD_PTR>(l_param));
+
   // Accessibility readers will send an OBJID_CLIENT message
-  if (kObjIdClient == l_param) {
+  if (OBJID_CLIENT == obj_id) {
     // Retrieve MSAA dispatch object for the root view.
     base::win::ScopedComPtr<IAccessible> root(
         delegate_->GetNativeViewAccessible());
 
     // Create a reference that MSAA will marshall to the client.
     reference_result = LresultFromObject(IID_IAccessible, w_param,
         static_cast<IAccessible*>(root.Detach()));
   }
 
   return reference_result;
@@ skipping 987 matching lines @@
     POINT cursor_pos = {0};
     ::GetCursorPos(&cursor_pos);
     if (memcmp(&cursor_pos, &mouse_location, sizeof(POINT)))
       return false;
     return true;
   }
   return false;
 }
 
 }  // namespace views