Send an empty tooltip text when hovering over a different node

third_party/WebKit/Source/core/page/ChromeClient.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple, Inc. All rights
  * reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 319 matching lines @@
 
   virtual std::unique_ptr<WebFrameScheduler> createFrameScheduler(
       BlameContext*) = 0;
 
   // Returns the time of the beginning of the last beginFrame, in seconds, if
   // any, and 0.0 otherwise.
   virtual double lastFrameTimeMonotonic() const { return 0.0; }
 
   virtual void installSupplements(LocalFrame&) {}
 
+  DECLARE_TRACE();
+
  protected:
   ~ChromeClient() override {}
 
   virtual void showMouseOverURL(const HitTestResult&) = 0;
   virtual void setWindowRect(const IntRect&, LocalFrame&) = 0;
   virtual bool openBeforeUnloadConfirmPanelDelegate(LocalFrame*,
                                                     bool isReload) = 0;
   virtual bool openJavaScriptAlertDelegate(LocalFrame*, const String&) = 0;
   virtual bool openJavaScriptConfirmDelegate(LocalFrame*, const String&) = 0;
   virtual bool openJavaScriptPromptDelegate(LocalFrame*,
                                             const String& message,
                                             const String& defaultValue,
                                             String& result) = 0;
   virtual void printDelegate(LocalFrame*) = 0;
 
  private:
   bool canOpenModalIfDuringPageDismissal(Frame* mainFrame,
                                          DialogType,
                                          const String& message);
   void setToolTip(LocalFrame&, const HitTestResult&);
 
+  WeakMember<Node> m_lastMouseOverNode;

[Stephen Chennney, 2017/01/03 20:38:25]

Does this really need to be a weak pointer, rather than a raw pointer? You only
ever use it for comparing the pointer value, never to access, so it seems to me
that a raw pointer would work.

   LayoutPoint m_lastToolTipPoint;
   String m_lastToolTipText;
 
   FRIEND_TEST_ALL_PREFIXES(ChromeClientTest, SetToolTipFlood);
 };
 
 }  // namespace blink
 
 #endif  // ChromeClient_h