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

SkRegion::Op --> SkCanvas::ClipOp (alias) --> SkClipOp

pre-CL needed in chrome : https://codereview.chromium.org/2355583002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2355483002

Review-Url: https://codereview.chromium.org/2355483002
diff --git a/src/utils/SkCanvasStateUtils.cpp b/src/utils/SkCanvasStateUtils.cpp
index 4ef5e2f..cc8ea43 100644
--- a/src/utils/SkCanvasStateUtils.cpp
+++ b/src/utils/SkCanvasStateUtils.cpp
@@ -142,15 +142,15 @@
     bool failed() { return fFailed; }
 
     // ClipVisitor
-    void clipRect(const SkRect& rect, SkRegion::Op op, bool antialias) override {
+    void clipRect(const SkRect& rect, SkCanvas::ClipOp op, bool antialias) override {
         fFailed |= antialias;
     }
 
-    void clipRRect(const SkRRect& rrect, SkRegion::Op op, bool antialias) override {
+    void clipRRect(const SkRRect& rrect, SkCanvas::ClipOp op, bool antialias) override {
         fFailed |= antialias;
     }
 
-    void clipPath(const SkPath&, SkRegion::Op, bool antialias) override {
+    void clipPath(const SkPath&, SkCanvas::ClipOp, bool antialias) override {
         fFailed |= antialias;
     }
 
@@ -284,7 +284,7 @@
     }
 
     canvas->setMatrix(matrix);
-    canvas->setClipRegion(clip);
+    canvas->clipRegion(clip, SkCanvas::kReplace_Op);
 }
 
 static SkCanvas* create_canvas_from_canvas_layer(const SkCanvasLayerState& layerState) {