Do not show a tooltip same as the previous one.

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

Index: third_party/WebKit/Source/core/page/ChromeClient.cpp
diff --git a/third_party/WebKit/Source/core/page/ChromeClient.cpp b/third_party/WebKit/Source/core/page/ChromeClient.cpp
index ac605312b7dd7d5df7401adf1fe9ecdd92d03755..89c71fea82d11e0100527ddc253ea19e0e147ace 100644
--- a/third_party/WebKit/Source/core/page/ChromeClient.cpp
+++ b/third_party/WebKit/Source/core/page/ChromeClient.cpp
@@ -167,9 +167,20 @@ void ChromeClient::setToolTip(const HitTestResult& result)
         }
     }
 
+    if (m_lastToolTipPoint == result.hitTestLocation().point() && m_lastToolTipText == toolTip)
+        return;
+    m_lastToolTipPoint = result.hitTestLocation().point();
+    m_lastToolTipText = toolTip;
     setToolTip(toolTip, toolTipDirection);
 }
 
+void ChromeClient::clearToolTip()
+{
+    // Do not check m_lastToolTip* and do not update them intentionally.
+    // We don't want to show tooltips with same content after clearToolTip().
+    setToolTip(String(), LTR);
+}
+
 void ChromeClient::print(LocalFrame* frame)
 {
     // Defer loads in case the client method runs a new event loop that would