Ensure Windows window classes are unregistered on shutdown (take 2)

chrome/browser/process_singleton_win.cc

 // Copyright (c) 2009 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 "chrome/browser/process_singleton.h"
 
 #include "base/base_paths.h"
 #include "base/command_line.h"
 #include "base/process_util.h"
 #include "base/win_util.h"
@@ skipping 27 matching lines @@
     : window_(NULL), locked_(false) {
   // FindWindoEx and Create() should be one atomic operation in order to not
   // have a race condition.
   remote_window_ = FindWindowEx(HWND_MESSAGE, NULL, chrome::kMessageWindowClass,
                                 user_data_dir.ToWStringHack().c_str());
   if (!remote_window_)
     Create();
 }
 
 ProcessSingleton::~ProcessSingleton() {
-  if (window_)
+  if (window_) {
     DestroyWindow(window_);
+    UnregisterClass(chrome::kMessageWindowClass, GetModuleHandle(NULL));
+  }
 }
 
 bool ProcessSingleton::NotifyOtherProcess() {
   if (!remote_window_)
     return false;
 
   // Found another window, send our command line to it
   // format is "START\0<<<current directory>>>\0<<<commandline>>>".
   std::wstring to_send(L"START\0", 6);  // want the NULL in the string.
   std::wstring cur_dir;
@@ skipping 75 matching lines @@
   if (window_)
     return;
 
   HINSTANCE hinst = GetModuleHandle(NULL);
 
   WNDCLASSEX wc = {0};
   wc.cbSize = sizeof(wc);
   wc.lpfnWndProc = ProcessSingleton::WndProcStatic;
   wc.hInstance = hinst;
   wc.lpszClassName = chrome::kMessageWindowClass;
-  RegisterClassEx(&wc);
+  ATOM clazz = RegisterClassEx(&wc);
+  DCHECK(clazz);
 
   std::wstring user_data_dir;
   PathService::Get(chrome::DIR_USER_DATA, &user_data_dir);
 
   // Set the window's title to the path of our user data directory so other
   // Chrome instances can decide if they should forward to us or not.
   window_ = CreateWindow(chrome::kMessageWindowClass, user_data_dir.c_str(),
                          0, 0, 0, 0, 0, HWND_MESSAGE, 0, hinst, 0);
   DCHECK(window_);
 
@@ skipping 94 matching lines @@
   switch (message) {
     case WM_COPYDATA:
       return OnCopyData(reinterpret_cast<HWND>(wparam),
                         reinterpret_cast<COPYDATASTRUCT*>(lparam));
     default:
       break;
   }
 
   return ::DefWindowProc(hwnd, message, wparam, lparam);
 }