Bug fix for cull_line in SkDashPathEffect.

src/effects/SkDashPathEffect.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 "SkDashPathEffect.h"
 
 #include "SkDashPathPriv.h"
@@ skipping 48 matching lines @@
                       const SkMatrix& ctm, const SkRect* cullRect,
                       const SkScalar intervalLength) {
     if (NULL == cullRect) {
         SkASSERT(false); // Shouldn't ever occur in practice
         return false;
     }
 
     SkScalar dx = pts[1].x() - pts[0].x();
     SkScalar dy = pts[1].y() - pts[0].y();
 
-    if (dx && dy) {
+    if ((dx && dy) || (!dx && !dy)) {
         return false;
     }
 
     SkRect bounds = *cullRect;
     outset_for_stroke(&bounds, rec);
 
     // cullRect is in device space while pts are in the local coordinate system
     // defined by the ctm. We want our answer in the local coordinate system.
 
     SkASSERT(ctm.rectStaysRect());
@@ skipping 326 matching lines @@
         }
     } else {
         // set the internal data members, fPhase should have been between 0 and intervalLength
         // when written to buffer so no need to adjust it
         SkDashPath::CalcDashParameters(fPhase, fIntervals, fCount,
                 &fInitialDashLength, &fInitialDashIndex, &fIntervalLength);
     }
 }
 #endif