Implement a Hit Test Cache.

Source/core/layout/LayoutView.h

Index: Source/core/layout/LayoutView.h
diff --git a/Source/core/layout/LayoutView.h b/Source/core/layout/LayoutView.h
index c8caad6cd3304c6b400cd9205dc77108cb594c81..04c942dcfce914ec8716411437b665fd723922c1 100644
--- a/Source/core/layout/LayoutView.h
+++ b/Source/core/layout/LayoutView.h
@@ -25,6 +25,7 @@
 #include "core/CoreExport.h"
 #include "core/dom/Position.h"
 #include "core/frame/FrameView.h"
+#include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/LayoutState.h"
 #include "core/layout/PaintInvalidationState.h"
@@ -51,11 +52,12 @@ public:
     void willBeDestroyed() override;
 
     bool hitTest(HitTestResult&);
-    bool hitTest(const HitTestRequest&, const HitTestLocation&, HitTestResult&);
 
     // Returns the total count of calls to HitTest, for testing.
     unsigned hitTestCount() const { return m_hitTestCount; }
 
+    void clearHitTestCache();
+
     virtual const char* name() const override { return "LayoutView"; }
 
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectLayoutView || LayoutBlockFlow::isOfType(type); }
@@ -123,7 +125,7 @@ public:
 
     LayoutState* layoutState() const { return m_layoutState; }
 
-    virtual void updateHitTestResult(HitTestResult&, const LayoutPoint&) override;
+    virtual void updateHitTestResult(HitTestResult&, const LayoutPoint&, const LayoutRect&) override;
 
     LayoutUnit pageLogicalHeight() const { return m_pageLogicalHeight; }
     void setPageLogicalHeight(LayoutUnit height)
@@ -206,6 +208,9 @@ private:
     unsigned m_layoutCounterCount;
 
     unsigned m_hitTestCount;
+    unsigned m_hitTestCacheHits;
+    HitTestResult m_hitTestCacheResult;
+    int m_hitTestCacheLayoutCount;
 
     OwnPtrWillBePersistent<PendingSelection> m_pendingSelection;
 };