ProcessSingleton now uses base::win::MessageWindow to create a message-only window.

chrome/common/chrome_constants.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 "chrome/common/chrome_constants.h"
 
 #include "base/files/file_path.h"
 
 #define FPL FILE_PATH_LITERAL
 
@@ skipping 120 matching lines @@
   FPL("NP"),  // No PIE
   NULL
 };
 #endif  // OS_MACOSX
 
 #if defined(OS_WIN)
 const base::FilePath::CharType kMetroDriverDll[] = FPL("metro_driver.dll");
 const wchar_t kStatusTrayWindowClass[] = L"Chrome_StatusTrayWindow";
 #endif  // defined(OS_WIN)
 
-const wchar_t kMessageWindowClass[] = L"Chrome_MessageWindow";
 const wchar_t kCrashReportLog[] = L"Reported Crashes.txt";
 const wchar_t kTestingInterfaceDLL[] = L"testing_interface.dll";
 const char    kInitialProfile[] = "Default";
 const char    kMultiProfileDirPrefix[] = "Profile ";
 const wchar_t kBrowserResourcesDll[] = L"chrome.dll";
 const base::FilePath::CharType kExtensionFileExtension[] = FPL(".crx");
 const base::FilePath::CharType kExtensionKeyFileExtension[] = FPL(".pem");
 
 // filenames
 #if defined(OS_ANDROID)
@@ skipping 99 matching lines @@
 const wchar_t kLaunchModeValue[] = L"launch_mode";
 #endif
 
 #if defined(OS_CHROMEOS)
 const char kProfileDirPrefix[] = "u-";
 #endif
 
 }  // namespace chrome
 
 #undef FPL