abort op early if path isn't parseable

src/pathops/SkPathOpsOp.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkAddIntersections.h"
 #include "SkOpEdgeBuilder.h"
 #include "SkPathOpsCommon.h"
 #include "SkPathWriter.h"
@@ skipping 252 matching lines @@
         subtrahend = &one;
         op = kDifference_PathOp;
     }
 #if DEBUG_SORT || DEBUG_SWAP_TOP
     SkPathOpsDebug::gSortCount = SkPathOpsDebug::gSortCountDefault;
 #endif
     // turn path into list of segments
     SkTArray<SkOpContour> contours;
     // FIXME: add self-intersecting cubics' T values to segment
     SkOpEdgeBuilder builder(*minuend, contours);
+    if (builder.unparseable()) {
+        return false;
+    }
     const int xorMask = builder.xorMask();
     builder.addOperand(*subtrahend);
     if (!builder.finish()) {
         return false;
     }
     result->reset();
     result->setFillType(fillType);
     const int xorOpMask = builder.xorMask();
     SkTArray<SkOpContour*, true> contourList;
     MakeContourList(contours, contourList, xorMask == kEvenOdd_PathOpsMask,
@@ skipping 31 matching lines @@
     {  // if some edges could not be resolved, assemble remaining fragments
         SkPath temp;
         temp.setFillType(fillType);
         SkPathWriter assembled(temp);
         Assemble(wrapper, &assembled);
         *result = *assembled.nativePath();
         result->setFillType(fillType);
     }
     return true;
 }