abstract name of clipping ops, to transtion to a more restricted set

src/utils/SkCanvasStack.cpp

Index: src/utils/SkCanvasStack.cpp
diff --git a/src/utils/SkCanvasStack.cpp b/src/utils/SkCanvasStack.cpp
index a5a483dac9c2f438dd5599475efffd66636a1304..58607d7d293466c3b89cb1b9927fddf93e0b1aef 100644
--- a/src/utils/SkCanvasStack.cpp
+++ b/src/utils/SkCanvasStack.cpp
@@ -53,7 +53,7 @@ void SkCanvasStack::removeAll() {
 void SkCanvasStack::clipToZOrderedBounds() {
     SkASSERT(fList.count() == fCanvasData.count());
     for (int i = 0; i < fList.count(); ++i) {
-        fList[i]->clipRegion(fCanvasData[i].requiredClip, SkRegion::kIntersect_Op);
+        fList[i]->clipRegion(fCanvasData[i].requiredClip);
     }
 }
 
@@ -76,22 +76,22 @@ void SkCanvasStack::didSetMatrix(const SkMatrix& matrix) {
     this->SkCanvas::didSetMatrix(matrix);
 }
 
-void SkCanvasStack::onClipRect(const SkRect& r, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
+void SkCanvasStack::onClipRect(const SkRect& r, ClipOp op, ClipEdgeStyle edgeStyle) {
     this->INHERITED::onClipRect(r, op, edgeStyle);
     this->clipToZOrderedBounds();
 }
 
-void SkCanvasStack::onClipRRect(const SkRRect& rr, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
+void SkCanvasStack::onClipRRect(const SkRRect& rr, ClipOp op, ClipEdgeStyle edgeStyle) {
     this->INHERITED::onClipRRect(rr, op, edgeStyle);
     this->clipToZOrderedBounds();
 }
 
-void SkCanvasStack::onClipPath(const SkPath& p, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
+void SkCanvasStack::onClipPath(const SkPath& p, ClipOp op, ClipEdgeStyle edgeStyle) {
     this->INHERITED::onClipPath(p, op, edgeStyle);
     this->clipToZOrderedBounds();
 }
 
-void SkCanvasStack::onClipRegion(const SkRegion& deviceRgn, SkRegion::Op op) {
+void SkCanvasStack::onClipRegion(const SkRegion& deviceRgn, ClipOp op) {
     SkASSERT(fList.count() == fCanvasData.count());
     for (int i = 0; i < fList.count(); ++i) {
         SkRegion tempRegion;