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

src/pdf/SkPDFCanvas.h

Index: src/pdf/SkPDFCanvas.h
diff --git a/src/pdf/SkPDFCanvas.h b/src/pdf/SkPDFCanvas.h
index 5040e9817d700459a64b14fc196a1c5285db14e5..ead13c34a555eabb7fad92afe3b3e4be8e3017a1 100644
--- a/src/pdf/SkPDFCanvas.h
+++ b/src/pdf/SkPDFCanvas.h
@@ -17,9 +17,9 @@ public:
     ~SkPDFCanvas();
 
 protected:
-    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 onClipRect(const SkRect&, ClipOp, ClipEdgeStyle) override;
+    void onClipRRect(const SkRRect&, ClipOp, ClipEdgeStyle) override;
+    void onClipPath(const SkPath&, ClipOp, ClipEdgeStyle) override;
 
     void onDrawBitmapNine(const SkBitmap&, const SkIRect&, const SkRect&,
                           const SkPaint*) override;