Make hit-test support clip-path references using svg clipPath

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 00fd49ac48a81fc9340041380d47c71dad147a54..387682afdb40a6c23843b55d8fdbedb3eefc92af 100644
--- a/Source/core/layout/LayoutBlock.cpp
+++ b/Source/core/layout/LayoutBlock.cpp
@@ -59,6 +59,7 @@
 #include "core/layout/line/InlineIterator.h"
 #include "core/layout/line/InlineTextBox.h"
 #include "core/layout/shapes/ShapeOutsideInfo.h"
+#include "core/layout/svg/LayoutSVGResourceClipper.h"
 #include "core/page/Page.h"
 #include "core/paint/BlockPainter.h"
 #include "core/paint/BoxPainter.h"
@@ -1690,7 +1691,13 @@ bool LayoutBlock::nodeAtPoint(HitTestResult& result, const HitTestLocation& loca
             break;
         }
         case ClipPathOperation::REFERENCE:
-            // FIXME: handle REFERENCE
+            ReferenceClipPathOperation* referenceClipPathOperation = toReferenceClipPathOperation(style()->clipPath());
+            Element* element = document().getElementById(referenceClipPathOperation->fragment());
+            if (element && isSVGClipPathElement(element) && element->layoutObject()) {

[fs, 2015/08/19 22:04:57]

Nit: The pointer-version of is...Element checks for null, so the explicit check
is redundant. Please drop.

[Yufeng Shen (Slow to review), 2015/08/20 20:17:21]

Done.

+                LayoutSVGResourceClipper* clipper = toLayoutSVGResourceClipper(toLayoutSVGResourceContainer(element->layoutObject()));
+                if (!clipper->hitTestClipContent(borderBoxRect(), FloatPoint(locationInContainer.point() - localOffset)))
+                    return false;
+            }
             break;
         }
     }