check for zero scale in SkDraw::ComputeResScaleForStroking

src/core/SkDraw.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.
  */
 #define __STDC_LIMIT_MACROS
 
 #include "SkDraw.h"
 #include "SkBlitter.h"
@@ skipping 988 matching lines @@
     SkPath path;
     path.addRRect(rrect);
     this->drawPath(path, paint, nullptr, true);
 }
 
 SkScalar SkDraw::ComputeResScaleForStroking(const SkMatrix& matrix) {
     if (!matrix.hasPerspective()) {
         SkScalar sx = SkPoint::Length(matrix[SkMatrix::kMScaleX], matrix[SkMatrix::kMSkewY]);
         SkScalar sy = SkPoint::Length(matrix[SkMatrix::kMSkewX],  matrix[SkMatrix::kMScaleY]);
         if (SkScalarsAreFinite(sx, sy)) {
-            return SkTMax(sx, sy);
+            SkScalar scale = SkTMax(sx, sy);
+            if (scale > 0) {
+                return scale;
+            }
         }
     }
     return 1;
 }
 
 void SkDraw::drawDevPath(const SkPath& devPath, const SkPaint& paint, bool drawCoverage,
                          SkBlitter* customBlitter, bool doFill) const {
     SkBlitter* blitter = nullptr;
     SkAutoBlitterChoose blitterStorage;
     if (nullptr == customBlitter) {
@@ skipping 1061 matching lines @@
         mask->fImage = SkMask::AllocImage(size);
         memset(mask->fImage, 0, mask->computeImageSize());
     }
 
     if (SkMask::kJustComputeBounds_CreateMode != mode) {
         draw_into_mask(*mask, devPath, style);
     }
 
     return true;
 }