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

The current implementation of base::MessagePumpForUI on Windows registers a window class with a predefined name in order to create a message-only window. The window class is unregistered when base::MessagePumpForUI is deleted. This causes issues when two or more instances of base::MessagePumpForUI are created/destroyed simultanenously on different threads. For instance once thread can unregister the window class right before the other thread is trying to create a window using this class.

The CL addresses this problem by switching MessageWindow to implement a message-only window. It also moves MessageWindow from remoting/host/win to base/win along with the corresponding unit test.

MessageWindow registers a uniquely named window class per MessageWindow instance making sure that different MessageWindow objects do not share any resources. In the future this can be optimized further by registering a common window class shared by all MessageWindow objects in a thread-safe manner (by using LazyInstance for example).

BUG=241939

Review URL: https://chromiumcodereview.appspot.com/15261005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@201955 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 13 insertions, 11 deletions

diff --git a/base/message_pump_win.h b/base/message_pump_win.h
index 5ea195f..67b076d 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<win::MessageWindow> window_;
 };
 
 //-----------------------------------------------------------------------------