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

chrome/browser/process_singleton.h

Index: chrome/browser/process_singleton.h
diff --git a/chrome/browser/process_singleton.h b/chrome/browser/process_singleton.h
index 737dabaf4cec8ce0b5fae0c5f90d8bc5a710b149..a584147d5f3759f8c8f096d2bb3c35f4cf035361 100644
--- a/chrome/browser/process_singleton.h
+++ b/chrome/browser/process_singleton.h
@@ -28,6 +28,10 @@
 #include "base/files/scoped_temp_dir.h"
 #endif  // defined(OS_LINUX) || defined(OS_OPENBSD)
 
+#if defined(OS_WIN)
+#include "base/win/message_window.h"
+#endif  // defined(OS_WIN)
+
 class CommandLine;
 
 // ProcessSingleton ----------------------------------------------------------
@@ -84,10 +88,6 @@ class ProcessSingleton : public base::NonThreadSafe {
   // Clear any lock state during shutdown.
   void Cleanup();
 
-#if defined(OS_WIN)
-  LRESULT WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
-#endif
-
 #if defined(OS_LINUX) || defined(OS_OPENBSD)
   static void DisablePromptForTesting();
 #endif  // defined(OS_LINUX) || defined(OS_OPENBSD)
@@ -123,13 +123,10 @@ class ProcessSingleton : public base::NonThreadSafe {
   NotificationCallback notification_callback_;  // Handler for notifications.
 
 #if defined(OS_WIN)
-  // This ugly behemoth handles startup commands sent from another process.
-  LRESULT OnCopyData(HWND hwnd, const COPYDATASTRUCT* cds);
-
   bool EscapeVirtualization(const base::FilePath& user_data_dir);
 
   HWND remote_window_;  // The HWND_MESSAGE of another browser.
-  HWND window_;  // The HWND_MESSAGE window.
+  base::win::MessageWindow window_;  // The message-only window.
   bool is_virtualized_;  // Stuck inside Microsoft Softricity VM environment.
   HANDLE lock_file_;
   base::FilePath user_data_dir_;