This fixes http://code.google.com/p/chromium/issues/detail?id=3007, which is ...

webkit/tools/test_shell/event_sending_controller.h

 // Copyright (c) 2006-2008 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.
 
 
 /*
   EventSendingController class:
   Bound to a JavaScript window.eventSender object using
   CppBoundClass::BindToJavascript(), this allows layout tests that are run in
   the test_shell to fire DOM events.
@@ skipping 53 matching lines @@
 
   // Returns true if dragMode is true.
   bool drag_mode() { return dragMode.isBool() && dragMode.ToBoolean(); }
 
   // Sometimes we queue up mouse move and mouse up events for drag drop
   // handling purposes.  These methods dispatch the event.
   static void DoMouseMove(const WebMouseEvent& e);
   static void DoMouseUp(const WebMouseEvent& e);
   static void ReplaySavedEvents();
 
-  // Helper to extract the optional arg from mouseDown() and mouseUp()
-  static WebMouseEvent::Button GetButtonTypeFromSingleArg(
-      const CppArgumentList& args);
+  // Helper to return the button type given a button code
+  static WebMouseEvent::Button GetButtonTypeFromButtonNumber(int button_code);
+
+  // Helper to extract the button number from the optional argument in
+  // mouseDown and mouseUp
+  static int GetButtonNumberFromSingleArg(const CppArgumentList& args);
 
   // Returns true if the key_code passed in needs a shift key modifier to
   // be passed into the generated event.
   bool NeedsShiftModifer(wchar_t key_code);
 
   // Non-owning pointer.  The LayoutTestController is owned by the host.
   static TestShell* shell_;
 
   // Location of last mouseMoveTo event.
   static gfx::Point last_mouse_pos_;
 
   // Currently pressed mouse button (Left/Right/Middle or None)
   static WebMouseEvent::Button pressed_button_;
+
+  // The last button number passed to mouseDown and mouseUp.
+  // Used to determine whether the click count continues to
+  // increment or not.
+  static int last_button_number_;
 };
 
 #endif  // WEBKIT_TOOLS_TEST_SHELL_EVENT_SENDING_CONTROLLER_H_