Making sure that base::MessagePumpForUI from different modules are isolated from each other.

base/message_pump_win.cc

Index: base/message_pump_win.cc
diff --git a/base/message_pump_win.cc b/base/message_pump_win.cc
index 9484b29e67c5cc00bd98e92e18a34e4f10e43c6b..2b40b6552d973c40b949f87bd46c4edd2ef7ef10 100644
--- a/base/message_pump_win.cc
+++ b/base/message_pump_win.cc
@@ -8,11 +8,13 @@
 
 #include "base/message_loop.h"
 #include "base/metrics/histogram.h"
+#include "base/process_util.h"
+#include "base/stringprintf.h"
 #include "base/win/wrapped_window_proc.h"
 
 namespace base {
 
-static const wchar_t kWndClass[] = L"Chrome_MessagePumpWindow";
+static const wchar_t kWndClassFormat[] = L"Chrome_MessagePumpWindow%p";
 
 // Message sent to get an additional time slice for pumping (processing) another
 // task (a series of such messages creates a continuous task pump).
@@ -82,13 +84,19 @@ int MessagePumpWin::GetCurrentDelay() const {
 //-----------------------------------------------------------------------------
 // MessagePumpForUI public:
 
-MessagePumpForUI::MessagePumpForUI() {
+MessagePumpForUI::MessagePumpForUI()
+  : atom_(0),
+    instance_(NULL),
+    message_hwnd_(NULL) {
   InitMessageWnd();
 }
 
 MessagePumpForUI::~MessagePumpForUI() {
-  DestroyWindow(message_hwnd_);
-  UnregisterClass(kWndClass, GetModuleHandle(NULL));
+  if (message_hwnd_ != NULL)

[jar (doing other things), 2012/05/17 00:57:24]

nit: you probably don't need this test.  The constructor does a CHECK in
InitMessageWnd()

+    DestroyWindow(message_hwnd_);
+
+  if (atom_ != 0)

[jar (doing other things), 2012/05/17 00:57:24]

nit: The test is not needed since the constructors ensures a non-zero value. You
could DCHECK if you're paranoid, or even CHECK.

+    UnregisterClass(MAKEINTATOM(atom_), instance_);
 }
 
 void MessagePumpForUI::ScheduleWork() {
@@ -230,18 +238,21 @@ void MessagePumpForUI::DoRunLoop() {
 }
 
 void MessagePumpForUI::InitMessageWnd() {
-  HINSTANCE hinst = GetModuleHandle(NULL);
+  // Register a unique window class for each instance of the UI pump.
+  string16 class_name = base::StringPrintf(kWndClassFormat, this);
 
   WNDCLASSEX wc = {0};
   wc.cbSize = sizeof(wc);
   wc.lpfnWndProc = base::win::WrappedWindowProc<WndProcThunk>;
-  wc.hInstance = hinst;
-  wc.lpszClassName = kWndClass;
-  RegisterClassEx(&wc);
-
-  message_hwnd_ =
-      CreateWindow(kWndClass, 0, 0, 0, 0, 0, 0, HWND_MESSAGE, 0, hinst, 0);
-  DCHECK(message_hwnd_);
+  instance_ = base::GetModuleFromAddress(static_cast<void*>(wc.lpfnWndProc));

[jar (doing other things), 2012/05/17 02:48:09]

Talking to rvargas, he notes that a "minimal" change would be to only fix this
one line, and all would be well.

You don't need the printf, etc.  That would make this notably smaller.... you
don't need atom... since the class name is constant, etc.

[alexeypa (please no reviews), 2012/05/17 18:30:19]

I guess you are right. Sure such a fix will not give us any additional checks
but we don't really have time, so that should be bake in trunk.

+  wc.hInstance = instance_;
+  wc.lpszClassName = class_name.c_str();
+  atom_ = RegisterClassEx(&wc);
+  CHECK(atom_ != 0);
+
+  message_hwnd_ = CreateWindow(
+      MAKEINTATOM(atom_), 0, 0, 0, 0, 0, 0, HWND_MESSAGE, 0, instance_, 0);
+  CHECK(message_hwnd_);
 }
 
 void MessagePumpForUI::WaitForWork() {