Add toSVGClipPathElement(), and use it

Source/core/rendering/svg/RenderSVGResourceClipper.cpp

Index: Source/core/rendering/svg/RenderSVGResourceClipper.cpp
diff --git a/Source/core/rendering/svg/RenderSVGResourceClipper.cpp b/Source/core/rendering/svg/RenderSVGResourceClipper.cpp
index 92a96dd39496417cc3831ae5ff8a3b8e389470fc..9da09f9d9f0c299df32978dd0d74385de5bcab12 100644
--- a/Source/core/rendering/svg/RenderSVGResourceClipper.cpp
+++ b/Source/core/rendering/svg/RenderSVGResourceClipper.cpp
@@ -127,7 +127,7 @@ bool RenderSVGResourceClipper::pathOnlyClipping(GraphicsContext* context, const
         }
     }
     // Only one visible shape/path was found. Directly continue clipping and transform the content to userspace if necessary.
-    if (static_cast<SVGClipPathElement*>(node())->clipPathUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
+    if (toSVGClipPathElement(node())->clipPathUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
         AffineTransform transform;
         transform.translate(objectBoundingBox.x(), objectBoundingBox.y());
         transform.scaleNonUniform(objectBoundingBox.width(), objectBoundingBox.height());
@@ -152,7 +152,7 @@ bool RenderSVGResourceClipper::applyClippingToContext(RenderObject* object, cons
         m_clipper.set(object, new ClipperData);
 
     bool shouldCreateClipData = false;
-    AffineTransform animatedLocalTransform = static_cast<SVGClipPathElement*>(node())->animatedLocalTransform();
+    AffineTransform animatedLocalTransform = toSVGClipPathElement(node())->animatedLocalTransform();
     ClipperData* clipperData = m_clipper.get(object);
     if (!clipperData->clipMaskImage) {
         if (pathOnlyClipping(context, animatedLocalTransform, objectBoundingBox))
@@ -208,8 +208,7 @@ bool RenderSVGResourceClipper::drawContentIntoMaskImage(ClipperData* clipperData
     ASSERT(maskContext);
 
     AffineTransform maskContentTransformation;
-    SVGClipPathElement* clipPath = static_cast<SVGClipPathElement*>(node());
-    if (clipPath->clipPathUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
+    if (toSVGClipPathElement(node())->clipPathUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
         maskContentTransformation.translate(objectBoundingBox.x(), objectBoundingBox.y());
         maskContentTransformation.scaleNonUniform(objectBoundingBox.width(), objectBoundingBox.height());
         maskContext->concatCTM(maskContentTransformation);
@@ -277,7 +276,7 @@ void RenderSVGResourceClipper::calculateClipContentRepaintRect()
              continue;
         m_clipBoundaries.unite(renderer->localToParentTransform().mapRect(renderer->repaintRectInLocalCoordinates()));
     }
-    m_clipBoundaries = static_cast<SVGClipPathElement*>(node())->animatedLocalTransform().mapRect(m_clipBoundaries);
+    m_clipBoundaries = toSVGClipPathElement(node())->animatedLocalTransform().mapRect(m_clipBoundaries);
 }
 
 bool RenderSVGResourceClipper::hitTestClipContent(const FloatRect& objectBoundingBox, const FloatPoint& nodeAtPoint)
@@ -286,7 +285,7 @@ bool RenderSVGResourceClipper::hitTestClipContent(const FloatRect& objectBoundin
     if (!SVGRenderSupport::pointInClippingArea(this, point))
         return false;
 
-    SVGClipPathElement* clipPathElement = static_cast<SVGClipPathElement*>(node());
+    SVGClipPathElement* clipPathElement = toSVGClipPathElement(node());
     if (clipPathElement->clipPathUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
         AffineTransform transform;
         transform.translate(objectBoundingBox.x(), objectBoundingBox.y());
@@ -320,7 +319,7 @@ FloatRect RenderSVGResourceClipper::resourceBoundingBox(RenderObject* object)
     if (m_clipBoundaries.isEmpty())
         calculateClipContentRepaintRect();
 
-    if (static_cast<SVGClipPathElement*>(node())->clipPathUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
+    if (toSVGClipPathElement(node())->clipPathUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
         FloatRect objectBoundingBox = object->objectBoundingBox();
         AffineTransform transform;
         transform.translate(objectBoundingBox.x(), objectBoundingBox.y());