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/SkDumpCanvas.cpp b/src/utils/SkDumpCanvas.cpp
index ca18864..fcb24d2 100644
--- a/src/utils/SkDumpCanvas.cpp
+++ b/src/utils/SkDumpCanvas.cpp
@@ -105,7 +105,7 @@
     }
 }
 
-static const char* toString(SkRegion::Op op) {
+static const char* toString(SkCanvas::ClipOp op) {
     static const char* gOpNames[] = {
         "DIFF", "SECT", "UNION", "XOR", "RDIFF", "REPLACE"
     };
@@ -258,7 +258,7 @@
     return kSoft_ClipEdgeStyle == edgeStyle ? "AA" : "BW";
 }
 
-void SkDumpCanvas::onClipRect(const SkRect& rect, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
+void SkDumpCanvas::onClipRect(const SkRect& rect, ClipOp op, ClipEdgeStyle edgeStyle) {
     SkString str;
     toString(rect, &str);
     this->dump(kClip_Verb, nullptr, "clipRect(%s %s %s)", str.c_str(), toString(op),
@@ -266,7 +266,7 @@
     this->INHERITED::onClipRect(rect, op, edgeStyle);
 }
 
-void SkDumpCanvas::onClipRRect(const SkRRect& rrect, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
+void SkDumpCanvas::onClipRRect(const SkRRect& rrect, ClipOp op, ClipEdgeStyle edgeStyle) {
     SkString str;
     toString(rrect, &str);
     this->dump(kClip_Verb, nullptr, "clipRRect(%s %s %s)", str.c_str(), toString(op),
@@ -274,7 +274,7 @@
     this->INHERITED::onClipRRect(rrect, op, edgeStyle);
 }
 
-void SkDumpCanvas::onClipPath(const SkPath& path, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
+void SkDumpCanvas::onClipPath(const SkPath& path, ClipOp op, ClipEdgeStyle edgeStyle) {
     SkString str;
     toString(path, &str);
     this->dump(kClip_Verb, nullptr, "clipPath(%s %s %s)", str.c_str(), toString(op),
@@ -282,7 +282,7 @@
     this->INHERITED::onClipPath(path, op, edgeStyle);
 }
 
-void SkDumpCanvas::onClipRegion(const SkRegion& deviceRgn, SkRegion::Op op) {
+void SkDumpCanvas::onClipRegion(const SkRegion& deviceRgn, ClipOp op) {
     SkString str;
     toString(deviceRgn, &str);
     this->dump(kClip_Verb, nullptr, "clipRegion(%s %s)", str.c_str(),