Implement a Hit Test Cache.

Source/core/layout/HitTestResult.cpp

Index: Source/core/layout/HitTestResult.cpp
diff --git a/Source/core/layout/HitTestResult.cpp b/Source/core/layout/HitTestResult.cpp
index 526b62251bedabe4ade35baa441731b865cd72f8..cc5c22bf32775b652327aa7ff02075221058f886 100644
--- a/Source/core/layout/HitTestResult.cpp
+++ b/Source/core/layout/HitTestResult.cpp
@@ -108,6 +108,7 @@ HitTestResult& HitTestResult::operator=(const HitTestResult& other)
     m_innerURLElement = other.URLElement();
     m_scrollbar = other.scrollbar();
     m_isOverWidget = other.isOverWidget();
+    m_validityRect = other.m_validityRect;
 
     // Only copy the NodeSet in case of list hit test.
     m_listBasedTestResult = adoptPtrWillBeNoop(other.m_listBasedTestResult ? new NodeSet(*other.m_listBasedTestResult) : 0);
@@ -115,6 +116,24 @@ HitTestResult& HitTestResult::operator=(const HitTestResult& other)
     return *this;
 }
 
+bool HitTestResult::equalForCacheability(const HitTestResult& other) const
+{
+    return m_hitTestRequest.equalForCacheability(other.m_hitTestRequest)
+        && m_innerNode == other.innerNode()
+        && m_innerPossiblyPseudoNode == other.innerPossiblyPseudoNode()
+        && m_pointInInnerNodeFrame == other.m_pointInInnerNodeFrame
+        && m_localPoint == other.localPoint()
+        && m_innerURLElement == other.URLElement()
+        && m_scrollbar == other.scrollbar()
+        && m_isOverWidget == other.isOverWidget();
+}
+
+void HitTestResult::cacheValues(const HitTestResult& other)
+{
+    *this = other;
+    m_hitTestRequest = other.m_hitTestRequest.type() & ~HitTestRequest::AvoidCache;
+}
+
 DEFINE_TRACE(HitTestResult)
 {
     visitor->trace(m_innerNode);
@@ -219,6 +238,12 @@ bool HitTestResult::isSelected() const
     return false;
 }
 
+void HitTestResult::setValidityRect(const LayoutRect& rect)
+{
+    ASSERT(!rect.isEmpty());
+    m_validityRect = rect;
+}
+
 String HitTestResult::spellingToolTip(TextDirection& dir) const
 {
     dir = LTR;