Randomize seed for SkDiscretePathEffect::filterPath()

src/effects/SkDiscretePathEffect.cpp

Index: src/effects/SkDiscretePathEffect.cpp
diff --git a/src/effects/SkDiscretePathEffect.cpp b/src/effects/SkDiscretePathEffect.cpp
index de834424df34fc661638fcbb7026bdc8214571a7..f6f91124479404330b1763370a51a70deb44f76d 100644
--- a/src/effects/SkDiscretePathEffect.cpp
+++ b/src/effects/SkDiscretePathEffect.cpp
@@ -20,9 +20,10 @@ static void Perterb(SkPoint* p, const SkVector& tangent, SkScalar scale) {
     *p += normal;
 }
 
-
-SkDiscretePathEffect::SkDiscretePathEffect(SkScalar segLength, SkScalar deviation)
-    : fSegLength(segLength), fPerterb(deviation)
+SkDiscretePathEffect::SkDiscretePathEffect(SkScalar segLength,
+                                           SkScalar deviation,
+                                           uint32_t seedAssist)
+    : fSegLength(segLength), fPerterb(deviation), fSeedAssist(seedAssist)
 {
 }
 
@@ -31,7 +32,10 @@ bool SkDiscretePathEffect::filterPath(SkPath* dst, const SkPath& src,
     bool doFill = rec->isFillStyle();
 
     SkPathMeasure   meas(src, doFill);
-    uint32_t        seed = SkScalarRoundToInt(meas.getLength());
+
+    /* Caller may supply their own seed assist, which by default is 0 */
+    uint32_t seed = fSeedAssist ^ SkScalarRoundToInt(meas.getLength());
+
     SkLCGRandom     rand(seed ^ ((seed << 16) | (seed >> 16)));
     SkScalar        scale = fPerterb;
     SkPoint         p;
@@ -75,9 +79,11 @@ void SkDiscretePathEffect::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeScalar(fSegLength);
     buffer.writeScalar(fPerterb);
+    buffer.writeUInt(fSeedAssist);
 }
 
 SkDiscretePathEffect::SkDiscretePathEffect(SkReadBuffer& buffer) {
     fSegLength = buffer.readScalar();
     fPerterb = buffer.readScalar();
+    fSeedAssist = buffer.readUInt();
 }