add arcto patheffect

include/effects/SkArcToPathEffect.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkArcToPathEffect_DEFINED
+#define SkArcToPathEffect_DEFINED
+
+#include "SkPathEffect.h"
+
+class SK_API SkArcToPathEffect : public SkPathEffect {
+public:
+    /** radius must be > 0 to have an effect. It specifies the distance from each corner
+        that should be "rounded".
+    */
+    static SkPathEffect* Create(SkScalar radius) {
+        if (radius <= 0) {
+            return NULL;
+        }
+        return SkNEW_ARGS(SkArcToPathEffect, (radius));
+    }
+
+    bool filterPath(SkPath* dst, const SkPath& src, SkStrokeRec*, const SkRect*) const SK_OVERRIDE;
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkArcToPathEffect)
+
+protected:
+    explicit SkArcToPathEffect(SkScalar radius);
+    virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
+
+private:
+    SkScalar fRadius;
+
+    typedef SkPathEffect INHERITED;
+};
+
+#endif