Randomize seed for SkDiscretePathEffect::filterPath()

include/effects/SkDiscretePathEffect.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDiscretePathEffect_DEFINED
 #define SkDiscretePathEffect_DEFINED
 
 #include "SkPathEffect.h"
 
 /** \class SkDiscretePathEffect
 
     This path effect chops a path into discrete segments, and randomly displaces them.
 */
 class SK_API SkDiscretePathEffect : public SkPathEffect {
 public:
     /** Break the path into segments of segLength length, and randomly move the endpoints
         away from the original path by a maximum of deviation.
         Note: works on filled or framed paths
     */
-    static SkDiscretePathEffect* Create(SkScalar segLength, SkScalar deviation) {
-        return SkNEW_ARGS(SkDiscretePathEffect, (segLength, deviation));
+    static SkDiscretePathEffect* Create(SkScalar segLength,
+                                        SkScalar deviation,
+                                        uint32_t seedAssist=1) {

[scroggo, 2014/06/09 14:01:04]

Please add a comment explaining what seedAssist does. (It might be worth noting
that filtering the same path multiple times will result in the same segments,
but a different seedAssist value can be used to get a different set of segments
for the same path.)

[rs.prinja, 2014/06/11 04:15:16]

Done.

+        return SkNEW_ARGS(SkDiscretePathEffect,
+                          (segLength, deviation, seedAssist));
     }
 
     virtual bool filterPath(SkPath* dst, const SkPath& src,
                             SkStrokeRec*, const SkRect*) const SK_OVERRIDE;
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkDiscretePathEffect)
 
 protected:
-    SkDiscretePathEffect(SkScalar segLength, SkScalar deviation);
+    SkDiscretePathEffect(SkScalar segLength,
+                         SkScalar deviation,
+                         uint32_t seedAssist);
     explicit SkDiscretePathEffect(SkReadBuffer&);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
 private:
     SkScalar fSegLength, fPerterb;
 
+    /* Caller-supplied 32 bit seed assist */
+    uint32_t fSeedAssist;
+
     typedef SkPathEffect INHERITED;
 };
 
 #endif