Do not show a tooltip same as the previous one.

third_party/WebKit/Source/core/input/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 3133 matching lines @@
     Element* elem = m_frame->document()->getElementByAccessKey(key.lower());
     if (!elem)
         return false;
     elem->accessKeyAction(false);
     return true;
 }
 
 bool EventHandler::keyEvent(const PlatformKeyboardEvent& initialKeyEvent)
 {
     RefPtrWillBeRawPtr<FrameView> protector(m_frame->view());
-    m_frame->chromeClient().setToolTip(String(), LTR);
+    m_frame->chromeClient().clearToolTip();
 
     if (initialKeyEvent.windowsVirtualKeyCode() == VK_CAPITAL)
         capsLockStateMayHaveChanged();
 
 #if OS(WIN)
     if (panScrollInProgress()) {
         // If a key is pressed while the panScroll is in progress then we want to stop
         if (initialKeyEvent.type() == PlatformEvent::KeyDown || initialKeyEvent.type() == PlatformEvent::RawKeyDown)
             stopAutoscroll();
 
@@ skipping 923 matching lines @@
 PlatformEvent::Modifiers EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return static_cast<PlatformEvent::Modifiers>(PlatformEvent::CtrlKey | PlatformEvent::AltKey);
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink