use ClipOp instead of SkRegion for clipping

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index a6f263f517dd387510638b00d7bba207e93cda4e..be514bcd2f4cf1cf4acd58fd500a77f98f5f9986 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -1335,6 +1335,31 @@ void SkCanvas::resetMatrix() {
 
 //////////////////////////////////////////////////////////////////////////////
 
+static SkRegion::Op clip2rgn(SkClipOp op) {
+    if (kIntersect_SkClipOp == op) {
+        return SkRegion::kIntersect_Op;
+    } else {
+        SkASSERT(kDifference_SkClipOp == op);
+        return SkRegion::kDifference_Op;
+    }
+}
+
+void SkCanvas::clipRect(const SkRect& rect, SkClipOp op, bool doAntiAlias) {
+    this->clipRect(rect, clip2rgn(op), doAntiAlias);
+}
+
+void SkCanvas::clipRRect(const SkRRect& rrect, SkClipOp op, bool doAntiAlias) {
+    this->clipRRect(rrect, clip2rgn(op), doAntiAlias);
+}
+
+void SkCanvas::clipPath(const SkPath& path, SkClipOp op, bool doAntiAlias) {
+    this->clipPath(path, clip2rgn(op), doAntiAlias);
+}
+
+void SkCanvas::clipRegion(const SkRegion& deviceRgn, SkClipOp op) {
+    this->clipRegion(deviceRgn, clip2rgn(op));
+}
+
 void SkCanvas::clipRect(const SkRect& rect, SkRegion::Op op, bool doAA) {
     ClipEdgeStyle edgeStyle = doAA ? kSoft_ClipEdgeStyle : kHard_ClipEdgeStyle;
     this->onClipRect(rect, op, edgeStyle);