Implement a Hit Test Cache.

Source/core/layout/line/InlineFlowBox.cpp

Index: Source/core/layout/line/InlineFlowBox.cpp
diff --git a/Source/core/layout/line/InlineFlowBox.cpp b/Source/core/layout/line/InlineFlowBox.cpp
index f81ae36630fef868145a7073fa9c1be0f8911085..0ecf2ea9f78baca86e67855bdc86d1c6b8079aea 100644
--- a/Source/core/layout/line/InlineFlowBox.cpp
+++ b/Source/core/layout/line/InlineFlowBox.cpp
@@ -975,8 +975,10 @@ bool InlineFlowBox::nodeAtPoint(HitTestResult& result, const HitTestLocation& lo
     LayoutRect overflowRect(visualOverflowRect(lineTop, lineBottom));
     flipForWritingMode(overflowRect);
     overflowRect.moveBy(accumulatedOffset);
-    if (!locationInContainer.intersects(overflowRect))
+    if (!locationInContainer.intersects(overflowRect)) {
+        result.shrinkValidityRect(overflowRect);
         return false;
+    }
 
     // We need to hit test both our inline children (InlineBoxes) and culled inlines
     // (LayoutObjects). We check our inlines in the same order as line layout but
@@ -992,7 +994,8 @@ bool InlineFlowBox::nodeAtPoint(HitTestResult& result, const HitTestLocation& lo
             continue;
 
         if (curr->nodeAtPoint(result, locationInContainer, accumulatedOffset, lineTop, lineBottom)) {
-            layoutObject().updateHitTestResult(result, locationInContainer.point() - toLayoutSize(accumulatedOffset));
+            // TODO(dtapuska): Calculate pos based on lineTop/lineBottom
+            layoutObject().updateHitTestResult(result, locationInContainer.point() - toLayoutSize(accumulatedOffset), result.validityRect());
             return true;
         }
 
@@ -1019,8 +1022,10 @@ bool InlineFlowBox::nodeAtPoint(HitTestResult& result, const HitTestLocation& lo
         LayoutRect borderRect = logicalFrameRect();
         borderRect.moveBy(accumulatedOffset);
         FloatRoundedRect border = layoutObject().style()->getRoundedBorderFor(borderRect, includeLogicalLeftEdge(), includeLogicalRightEdge());
-        if (!locationInContainer.intersects(border))
+        if (!locationInContainer.intersects(border)) {
+            result.shrinkValidityRect(borderRect);
             return false;
+        }
     }
 
     // Now check ourselves. Pixel snap hit testing.
@@ -1047,10 +1052,11 @@ bool InlineFlowBox::nodeAtPoint(HitTestResult& result, const HitTestLocation& lo
     rect.moveBy(accumulatedOffset);
 
     if (visibleToHitTestRequest(result.hitTestRequest()) && locationInContainer.intersects(rect)) {
-        layoutObject().updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - toLayoutSize(accumulatedOffset))); // Don't add in m_x or m_y here, we want coords in the containing block's space.
+        layoutObject().updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - toLayoutSize(accumulatedOffset)), rect); // Don't add in m_x or m_y here, we want coords in the containing block's space.
         if (!result.addNodeToListBasedTestResult(layoutObject().node(), locationInContainer, rect))
             return true;
     }
+    result.shrinkValidityRect(rect);
 
     return false;
 }