Implement a Hit Test Cache.

Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/EffectModel.idl',
             'animation/AnimationEffectReadOnly.idl',
@@ skipping 539 matching lines @@
             'layout/BidiRunForLine.h',
             'layout/ClipRect.cpp',
             'layout/ClipRect.h',
             'layout/ClipRects.h',
             'layout/ClipRectsCache.h',
             'layout/CounterNode.cpp',
             'layout/CounterNode.h',
             'layout/FloatingObjects.cpp',
             'layout/FloatingObjects.h',
             'layout/GeneratedChildren.h',
+            'layout/HitTestCache.cpp',
+            'layout/HitTestCache.h',
             'layout/HitTestLocation.cpp',
             'layout/HitTestLocation.h',
             'layout/HitTestResult.cpp',
             'layout/HitTestingTransformState.cpp',
             'layout/HitTestingTransformState.h',
             'layout/ImageQualityController.cpp',
             'layout/ImageQualityController.h',
             'layout/LayoutState.cpp',
             'layout/OrderIterator.cpp',
             'layout/OrderIterator.h',
@@ skipping 3366 matching lines @@
             'style/OutlineValueTest.cpp',
             'style/SVGComputedStyleTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }