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

src/utils/SkCanvasStack.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvasStack_DEFINED
 #define SkCanvasStack_DEFINED
 
@@ skipping 13 matching lines @@
      * that do not make sense in the context of our CanvasStack, but since we
      * can share most of the other implementation of NWay we override those
      * methods to be no-ops.
      */
     void addCanvas(SkCanvas*) override { SkDEBUGFAIL("Invalid Op"); }
     void removeCanvas(SkCanvas*) override { SkDEBUGFAIL("Invalid Op"); }
 
 protected:
     void didSetMatrix(const SkMatrix&) override;
 
-    void onClipRect(const SkRect&, SkRegion::Op, ClipEdgeStyle) override;
-    void onClipRRect(const SkRRect&, SkRegion::Op, ClipEdgeStyle) override;
-    void onClipPath(const SkPath&, SkRegion::Op, ClipEdgeStyle) override;
-    void onClipRegion(const SkRegion&, SkRegion::Op) override;
+    void onClipRect(const SkRect&, ClipOp, ClipEdgeStyle) override;
+    void onClipRRect(const SkRRect&, ClipOp, ClipEdgeStyle) override;
+    void onClipPath(const SkPath&, ClipOp, ClipEdgeStyle) override;
+    void onClipRegion(const SkRegion&, ClipOp) override;
 
 private:
     void clipToZOrderedBounds();
 
     struct CanvasData {
         SkIPoint origin;
         SkRegion requiredClip;
     };
 
     SkTArray<CanvasData> fCanvasData;
 
     typedef SkNWayCanvas INHERITED;
 };
 
 #endif