allow one zero length dash

src/utils/SkDashPathPriv.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 SkDashPathPriv_DEFINED
 #define SkDashPathPriv_DEFINED
 
 #include "SkPathEffect.h"
 
 namespace SkDashPath {
     /*
      * Calculates the initialDashLength, initialDashIndex, and intervalLength based on the
      * inputed phase and intervals. If adjustedPhase is passed in, then the phase will be
      * adjusted to be between 0 and intervalLength. The result will be stored in adjustedPhase.
      * If adjustedPhase is nullptr then it is assumed phase is already between 0 and intervalLength
+     *
+     * Caller should have already used ValidDashPath to exclude invalid data.
      */
     void CalcDashParameters(SkScalar phase, const SkScalar intervals[], int32_t count,
                             SkScalar* initialDashLength, int32_t* initialDashIndex,
                             SkScalar* intervalLength, SkScalar* adjustedPhase = nullptr);
 
     bool FilterDashPath(SkPath* dst, const SkPath& src, SkStrokeRec*, const SkRect*,
-                        const SkScalar aIntervals[], int32_t count, SkScalar initialDashLength,
-                        int32_t initialDashIndex, SkScalar intervalLength);
-    
-    bool FilterDashPath(SkPath* dst, const SkPath& src, SkStrokeRec*, const SkRect*,
                         const SkPathEffect::DashInfo& info);
+
+    /*
+     * Caller should have already used ValidDashPath to exclude invalid data.
+     */
+    bool InternalFilter(SkPath* dst, const SkPath& src, SkStrokeRec* rec,
+                        const SkRect* cullRect, const SkScalar aIntervals[],
+                        int32_t count, SkScalar initialDashLength, int32_t initialDashIndex,
+                        SkScalar intervalLength);
+
+    bool ValidDashPath(SkScalar phase, const SkScalar intervals[], int32_t count);
 }
 
 #endif