Implement a Hit Test Cache.

Source/core/layout/LayoutBlock.cpp

Index: Source/core/layout/LayoutBlock.cpp
diff --git a/Source/core/layout/LayoutBlock.cpp b/Source/core/layout/LayoutBlock.cpp
index d1a61fd3345cb31e0d994a61f1afe1da5ef30bfa..fe86cd64c2006622879af6ce5e39ee6d6f95237c 100644
--- a/Source/core/layout/LayoutBlock.cpp
+++ b/Source/core/layout/LayoutBlock.cpp
@@ -2158,14 +2158,18 @@ bool LayoutBlock::nodeAtPoint(HitTestResult& result, const HitTestLocation& loca
         LayoutRect overflowBox = hasOverflowClip() ? borderBoxRect() : visualOverflowRect();
         flipForWritingMode(overflowBox);
         overflowBox.moveBy(adjustedLocation);
-        if (!locationInContainer.intersects(overflowBox))
+        if (!locationInContainer.intersects(overflowBox)) {
+            result.shrinkValidityRect(overflowBox);
             return false;
+        }
     }
 
     if ((hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground)
         && visibleToHitTestRequest(result.hitTestRequest())
         && isPointInOverflowControl(result, locationInContainer.point(), adjustedLocation)) {
-        updateHitTestResult(result, locationInContainer.point() - localOffset);
+        // TODO(dtapuska): calculate the layout rect
+
+        updateHitTestResult(result, locationInContainer.point() - localOffset, result.validityRect());
         // FIXME: isPointInOverflowControl() doesn't handle rect-based tests yet.
         if (!result.addNodeToListBasedTestResult(nodeForHitTest(), locationInContainer))
             return true;
@@ -2191,15 +2195,21 @@ bool LayoutBlock::nodeAtPoint(HitTestResult& result, const HitTestLocation& loca
     bool useClip = (hasControlClip() || useOverflowClip);
     bool checkChildren = !useClip;
     if (!checkChildren) {
+        LayoutRect clipRect;
         if (hasControlClip()) {
-            checkChildren = locationInContainer.intersects(controlClipRect(adjustedLocation));
+            clipRect = controlClipRect(adjustedLocation);
+            checkChildren = locationInContainer.intersects(clipRect);
         } else {
-            LayoutRect clipRect = overflowClipRect(adjustedLocation, IncludeOverlayScrollbarSize);
+            clipRect = overflowClipRect(adjustedLocation, IncludeOverlayScrollbarSize);
             if (style()->hasBorderRadius())
                 checkChildren = locationInContainer.intersects(style()->getRoundedBorderFor(clipRect));
             else
                 checkChildren = locationInContainer.intersects(clipRect);
         }
+        if (!checkChildren)
+            result.shrinkValidityRect(clipRect);
+        else
+            result.intersectValidityRect(clipRect);
     }
     if (checkChildren) {
         // Hit test descendants first.
@@ -2210,13 +2220,16 @@ bool LayoutBlock::nodeAtPoint(HitTestResult& result, const HitTestLocation& loca
         // Hit test contents if we don't have columns.
         if (!hasColumns()) {
             if (hitTestContents(result, locationInContainer, toLayoutPoint(scrolledOffset), hitTestAction)) {
-                updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
+                // TODO(dtapuska): calculate the layout rect
+
+                updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset), result.validityRect());
                 return true;
             }
             if (hitTestAction == HitTestFloat && hitTestFloats(result, locationInContainer, toLayoutPoint(scrolledOffset)))
                 return true;
         } else if (hitTestColumns(result, locationInContainer, toLayoutPoint(scrolledOffset), hitTestAction)) {
-            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
+            // TODO(dtapuska): calculate the layout rect
+            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset), result.validityRect());
             return true;
         }
     }
@@ -2226,18 +2239,21 @@ bool LayoutBlock::nodeAtPoint(HitTestResult& result, const HitTestLocation& loca
         LayoutRect borderRect = borderBoxRect();
         borderRect.moveBy(adjustedLocation);
         FloatRoundedRect border = style()->getRoundedBorderFor(borderRect);
-        if (!locationInContainer.intersects(border))
+        if (!locationInContainer.intersects(border)) {
+            result.shrinkValidityRect(borderRect);
             return false;
+        }
     }
 
     // Now hit test our background
     if (hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) {
         LayoutRect boundsRect(adjustedLocation, size());
         if (visibleToHitTestRequest(result.hitTestRequest()) && locationInContainer.intersects(boundsRect)) {
-            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
+            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset), boundsRect);
             if (!result.addNodeToListBasedTestResult(nodeForHitTest(), locationInContainer, boundsRect))
                 return true;
         }
+        result.shrinkValidityRect(boundsRect);
     }
 
     return false;
@@ -3487,11 +3503,12 @@ void LayoutBlock::childBecameNonInline(LayoutObject*)
     // |this| may be dead here
 }
 
-void LayoutBlock::updateHitTestResult(HitTestResult& result, const LayoutPoint& point)
+void LayoutBlock::updateHitTestResult(HitTestResult& result, const LayoutPoint& point, const LayoutRect& rect)
 {
     if (result.innerNode())
         return;
 
+    result.intersectValidityRect(rect);
     if (Node* n = nodeForHitTest())
         result.setNodeAndPosition(n, point);
 }