Implement a Hit Test Cache.

Source/core/layout/LayoutBlockFlow.cpp

Index: Source/core/layout/LayoutBlockFlow.cpp
diff --git a/Source/core/layout/LayoutBlockFlow.cpp b/Source/core/layout/LayoutBlockFlow.cpp
index d5aa6480168454a965083e47349e587897ca1998..ef122416ab704391c10a134526294645835ee6b7 100644
--- a/Source/core/layout/LayoutBlockFlow.cpp
+++ b/Source/core/layout/LayoutBlockFlow.cpp
@@ -2666,7 +2666,8 @@ bool LayoutBlockFlow::hitTestFloats(HitTestResult& result, const HitTestLocation
             LayoutUnit yOffset = yPositionForFloatIncludingMargin(floatingObject) - floatingObject->layoutObject()->location().y();
             LayoutPoint childPoint = flipFloatForWritingModeForChild(floatingObject, adjustedLocation + LayoutSize(xOffset, yOffset));
             if (floatingObject->layoutObject()->hitTest(result, locationInContainer, childPoint)) {
-                updateHitTestResult(result, locationInContainer.point() - toLayoutSize(childPoint));
+                // TODO(dtapuska): calculate the layout rect
+                updateHitTestResult(result, locationInContainer.point() - toLayoutSize(childPoint), result.validityRect());
                 return true;
             }
         }