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 84e6dc112d581cd23546e2c4f697da907183033d..83690358f760063f492084f24189d65037c335e0 100644
--- a/Source/core/layout/HitTestResult.cpp
+++ b/Source/core/layout/HitTestResult.cpp
@@ -101,6 +101,31 @@ HitTestResult& HitTestResult::operator=(const HitTestResult& other)
 {
     m_hitTestLocation = other.m_hitTestLocation;
     m_hitTestRequest = other.m_hitTestRequest;
+    populateFromCachedResult(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;
+}
+
+void HitTestResult::populateFromCachedResult(const HitTestResult& other)
+{
     m_innerNode = other.innerNode();
     m_innerPossiblyPseudoNode = other.innerPossiblyPseudoNode();
     m_pointInInnerNodeFrame = other.m_pointInInnerNodeFrame;
@@ -108,11 +133,10 @@ 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);
-
-    return *this;
 }
 
 DEFINE_TRACE(HitTestResult)
@@ -219,6 +243,12 @@ 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;