Allow multiple base::MessagePumpForUI instances to be created simultanenously on Windows.

base/message_pump_win.h

Index: base/message_pump_win.h
diff --git a/base/message_pump_win.h b/base/message_pump_win.h
index 5ea195fb15ac87d9944b9a8b1121556e671364e7..ed562ce0686931c799b17c00b9edd4fc82281a90 100644
--- a/base/message_pump_win.h
+++ b/base/message_pump_win.h
@@ -17,6 +17,7 @@
 #include "base/message_pump_observer.h"
 #include "base/observer_list.h"
 #include "base/time.h"
+#include "base/win/message_window.h"
 #include "base/win/scoped_handle.h"
 
 namespace base {
@@ -125,7 +126,9 @@ class BASE_EXPORT MessagePumpWin : public MessagePump {
 // an excellent choice.  It is also helpful that the starter messages that are
 // placed in the queue when new task arrive also awakens DoRunLoop.
 //
-class BASE_EXPORT MessagePumpForUI : public MessagePumpWin {
+class BASE_EXPORT MessagePumpForUI
+    : public MessagePumpWin,
+      public win::MessageWindow::Delegate {
  public:
   // A MessageFilter implements the common Peek/Translate/Dispatch code to deal
   // with windows messages.
@@ -175,12 +178,14 @@ class BASE_EXPORT MessagePumpForUI : public MessagePumpWin {
   void PumpOutPendingPaintMessages();
 
  private:
-  static LRESULT CALLBACK WndProcThunk(HWND window_handle,
-                                       UINT message,
-                                       WPARAM wparam,
-                                       LPARAM lparam);
+  // win::MessageWindow::Delegate interface.
+  virtual bool HandleMessage(HWND hwnd,
+                             UINT message,
+                             WPARAM wparam,
+                             LPARAM lparam,
+                             LRESULT* result) OVERRIDE;
+
   virtual void DoRunLoop();
-  void InitMessageWnd();
   void WaitForWork();
   void HandleWorkMessage();
   void HandleTimerMessage();
@@ -188,13 +193,10 @@ class BASE_EXPORT MessagePumpForUI : public MessagePumpWin {
   bool ProcessMessageHelper(const MSG& msg);
   bool ProcessPumpReplacementMessage();
 
-  // Instance of the module containing the window procedure.
-  HMODULE instance_;
+  scoped_ptr<MessageFilter> message_filter_;
 
   // A hidden message-only window.
-  HWND message_hwnd_;
-
-  scoped_ptr<MessageFilter> message_filter_;
+  scoped_ptr<base::win::MessageWindow> window_;
 };
 
 //-----------------------------------------------------------------------------