Fix use after free in HWNDMessageHandler

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 1434 matching lines @@
         static_cast<IAccessible*>(root.Detach()));
   }
 
   return reference_result;
 }
 
 LRESULT HWNDMessageHandler::OnImeMessages(UINT message,
                                           WPARAM w_param,
                                           LPARAM l_param) {
   LRESULT result = 0;
-  SetMsgHandled(delegate_->HandleIMEMessage(
-      message, w_param, l_param, &result));
+  base::WeakPtr<HWNDMessageHandler> ref(weak_factory_.GetWeakPtr());
+  const bool msg_handled =
+      delegate_->HandleIMEMessage(message, w_param, l_param, &result);
+  if (ref.get())
+    SetMsgHandled(msg_handled);
   return result;
 }
 
 void HWNDMessageHandler::OnInitMenu(HMENU menu) {
   bool is_fullscreen = fullscreen_handler_->fullscreen();
   bool is_minimized = IsMinimized();
   bool is_maximized = IsMaximized();
   bool is_restored = !is_fullscreen && !is_minimized && !is_maximized;
 
   ScopedRedrawLock lock(this);
@@ skipping 993 matching lines @@
     SetWindowPos(hwnd(), NULL, 0, 0, 0, 0, flags | SWP_HIDEWINDOW);
     SetWindowPos(hwnd(), NULL, 0, 0, 0, 0, flags | SWP_SHOWWINDOW);
   }
   // WM_DWMCOMPOSITIONCHANGED is only sent to top level windows, however we want
   // to notify our children too, since we can have MDI child windows who need to
   // update their appearance.
   EnumChildWindows(hwnd(), &SendDwmCompositionChanged, NULL);
 }
 
 }  // namespace views