check for bad params sent to discrete patheffect

src/effects/SkDiscretePathEffect.cpp

 /*
  * 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.
  */
 
 
 #include "SkDiscretePathEffect.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 #include "SkPathMeasure.h"
 #include "SkStrokeRec.h"
 
 sk_sp<SkPathEffect> SkDiscretePathEffect::Make(SkScalar segLength, SkScalar deviation,
                                                uint32_t seedAssist) {
+    if (!SkScalarIsFinite(segLength) || !SkScalarIsFinite(deviation)) {
+        return nullptr;
+    }
+    if (segLength <= SK_ScalarNearlyZero) {
+        return nullptr;
+    }
     return sk_sp<SkPathEffect>(new SkDiscretePathEffect(segLength, deviation, seedAssist));
 }
 
 static void Perterb(SkPoint* p, const SkVector& tangent, SkScalar scale) {
     SkVector normal = tangent;
     normal.rotateCCW();
     normal.setLength(scale);
     *p += normal;
 }
 
@@ skipping 107 matching lines @@
     buffer.writeUInt(fSeedAssist);
 }
 
 #ifndef SK_IGNORE_TO_STRING
 void SkDiscretePathEffect::toString(SkString* str) const {
     str->appendf("SkDiscretePathEffect: (");
     str->appendf("segLength: %.2f deviation: %.2f seed %d", fSegLength, fPerterb, fSeedAssist);
     str->append(")");
 }
 #endif