Implement a Hit Test Cache.

Source/core/layout/LayoutTableRow.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 187 matching lines @@
     // Table rows cannot ever be hit tested.  Effectively they do not exist.
     // Just forward to our children always.
     for (LayoutTableCell* cell = lastCell(); cell; cell = cell->previousCell()) {
         // FIXME: We have to skip over inline flows, since they can show up inside table rows
         // at the moment (a demoted inline <form> for example). If we ever implement a
         // table-specific hit-test method (which we should do for performance reasons anyway),
         // then we can remove this check.
         if (!cell->hasSelfPaintingLayer()) {
             LayoutPoint cellPoint = flipForWritingModeForChild(cell, accumulatedOffset);
             if (cell->nodeAtPoint(result, locationInContainer, cellPoint, action)) {
-                updateHitTestResult(result, locationInContainer.point() - toLayoutSize(cellPoint));
+                // TODO(dtapuska): Fix correct cell layout rect.
+                updateHitTestResult(result, locationInContainer.point() - toLayoutSize(cellPoint), result.validityRect());
                 return true;
             }
         }
     }
 
     return false;
 }
 
 void LayoutTableRow::paint(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
@@ skipping 33 matching lines @@
     // The cell and the row share the section's coordinate system. However
     // the visual overflow should be determined in the coordinate system of
     // the row, that's why we shift it below.
     LayoutUnit cellOffsetLogicalTopDifference = cell->location().y() - location().y();
     cellVisualOverflowRect.move(0, cellOffsetLogicalTopDifference);
 
     addVisualOverflow(cellVisualOverflowRect);
 }
 
 } // namespace blink