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/pipe/SkPipeReader.cpp b/src/pipe/SkPipeReader.cpp
index e0ca373..7157813 100644
--- a/src/pipe/SkPipeReader.cpp
+++ b/src/pipe/SkPipeReader.cpp
@@ -268,21 +268,21 @@
 
 static void clipRect_handler(SkPipeReader& reader, uint32_t packedVerb, SkCanvas* canvas) {
     SkASSERT(SkPipeVerb::kClipRect == unpack_verb(packedVerb));
-    SkRegion::Op op = (SkRegion::Op)(unpack_verb_extra(packedVerb) >> 1);
+    SkCanvas::ClipOp op = (SkCanvas::ClipOp)(unpack_verb_extra(packedVerb) >> 1);
     bool isAA = unpack_verb_extra(packedVerb) & 1;
     canvas->clipRect(*skip<SkRect>(reader), op, isAA);
 }
 
 static void clipRRect_handler(SkPipeReader& reader, uint32_t packedVerb, SkCanvas* canvas) {
     SkASSERT(SkPipeVerb::kClipRRect == unpack_verb(packedVerb));
-    SkRegion::Op op = (SkRegion::Op)(unpack_verb_extra(packedVerb) >> 1);
+    SkCanvas::ClipOp op = (SkCanvas::ClipOp)(unpack_verb_extra(packedVerb) >> 1);
     bool isAA = unpack_verb_extra(packedVerb) & 1;
     canvas->clipRRect(read_rrect(reader), op, isAA);
 }
 
 static void clipPath_handler(SkPipeReader& reader, uint32_t packedVerb, SkCanvas* canvas) {
     SkASSERT(SkPipeVerb::kClipPath == unpack_verb(packedVerb));
-    SkRegion::Op op = (SkRegion::Op)(unpack_verb_extra(packedVerb) >> 1);
+    SkCanvas::ClipOp op = (SkCanvas::ClipOp)(unpack_verb_extra(packedVerb) >> 1);
     bool isAA = unpack_verb_extra(packedVerb) & 1;
     SkPath path;
     reader.readPath(&path);
@@ -291,7 +291,7 @@
 
 static void clipRegion_handler(SkPipeReader& reader, uint32_t packedVerb, SkCanvas* canvas) {
     SkASSERT(SkPipeVerb::kClipRegion == unpack_verb(packedVerb));
-    SkRegion::Op op = (SkRegion::Op)(unpack_verb_extra(packedVerb) >> 1);
+    SkCanvas::ClipOp op = (SkCanvas::ClipOp)(unpack_verb_extra(packedVerb) >> 1);
     SkRegion region;
     reader.readRegion(&region);
     canvas->clipRegion(region, op);