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/gm/simpleaaclip.cpp b/gm/simpleaaclip.cpp
index b5aa3ae..87dc687 100644
--- a/gm/simpleaaclip.cpp
+++ b/gm/simpleaaclip.cpp
@@ -67,12 +67,12 @@
         INHERITED::setBGColor(sk_tool_utils::color_to_565(0xFFDDDDDD));
     }
 
-    void buildRgn(SkAAClip* clip, SkRegion::Op op) {
+    void buildRgn(SkAAClip* clip, SkCanvas::ClipOp op) {
         clip->setPath(fBasePath, nullptr, true);
 
         SkAAClip clip2;
         clip2.setPath(fRectPath, nullptr, true);
-        clip->op(clip2, op);
+        clip->op(clip2, (SkRegion::Op)op);
     }
 
     void drawOrig(SkCanvas* canvas) {
@@ -85,7 +85,7 @@
         canvas->drawRect(fRect, paint);
     }
 
-    void drawRgnOped(SkCanvas* canvas, SkRegion::Op op, SkColor color) {
+    void drawRgnOped(SkCanvas* canvas, SkCanvas::ClipOp op, SkColor color) {
 
         SkAAClip clip;
 
@@ -97,7 +97,7 @@
         paint_rgn(canvas, clip, paint);
     }
 
-    void drawPathsOped(SkCanvas* canvas, SkRegion::Op op, SkColor color) {
+    void drawPathsOped(SkCanvas* canvas, SkCanvas::ClipOp op, SkColor color) {
 
         this->drawOrig(canvas);
 
@@ -106,11 +106,11 @@
         // create the clip mask with the supplied boolean op
         if (kPath_GeomType == fGeomType) {
             // path-based case
-            canvas->clipPath(fBasePath, SkRegion::kReplace_Op, true);
+            canvas->clipPath(fBasePath, SkCanvas::kReplace_Op, true);
             canvas->clipPath(fRectPath, op, true);
         } else {
             // rect-based case
-            canvas->clipRect(fBase, SkRegion::kReplace_Op, true);
+            canvas->clipRect(fBase, SkCanvas::kReplace_Op, true);
             canvas->clipRect(fRect, op, true);
         }
 
@@ -144,14 +144,14 @@
         const struct {
             SkColor         fColor;
             const char*     fName;
-            SkRegion::Op    fOp;
+            SkCanvas::ClipOp fOp;
         } gOps[] = {
-            { SK_ColorBLACK,    "Difference", SkRegion::kDifference_Op    },
-            { SK_ColorRED,      "Intersect",  SkRegion::kIntersect_Op     },
-            { sk_tool_utils::color_to_565(0xFF008800), "Union", SkRegion::kUnion_Op },
-            { SK_ColorGREEN,    "Rev Diff",   SkRegion::kReverseDifference_Op },
-            { SK_ColorYELLOW,   "Replace",    SkRegion::kReplace_Op       },
-            { SK_ColorBLUE,     "XOR",        SkRegion::kXOR_Op           },
+            { SK_ColorBLACK,    "Difference", SkCanvas::kDifference_Op    },
+            { SK_ColorRED,      "Intersect",  SkCanvas::kIntersect_Op     },
+            { sk_tool_utils::color_to_565(0xFF008800), "Union", SkCanvas::kUnion_Op },
+            { SK_ColorGREEN,    "Rev Diff",   SkCanvas::kReverseDifference_Op },
+            { SK_ColorYELLOW,   "Replace",    SkCanvas::kReplace_Op       },
+            { SK_ColorBLUE,     "XOR",        SkCanvas::kXOR_Op           },
         };
 
         SkPaint textPaint;