allow conic chop to fail

src/core/SkGeometry.h

 /*
  * 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.
  */
 
 #ifndef SkGeometry_DEFINED
 #define SkGeometry_DEFINED
 
@@ skipping 197 matching lines @@
     }
 
     /**
      *  Given a t-value [0...1] return its position and/or tangent.
      *  If pos is not null, return its position at the t-value.
      *  If tangent is not null, return its tangent at the t-value. NOTE the
      *  tangent value's length is arbitrary, and only its direction should
      *  be used.
      */
     void evalAt(SkScalar t, SkPoint* pos, SkVector* tangent = nullptr) const;
-    void chopAt(SkScalar t, SkConic dst[2]) const;
+    bool SK_WARN_UNUSED_RESULT chopAt(SkScalar t, SkConic dst[2]) const;
     void chopAt(SkScalar t1, SkScalar t2, SkConic* dst) const;
     void chop(SkConic dst[2]) const;
 
     SkPoint evalAt(SkScalar t) const;
     SkVector evalTangentAt(SkScalar t) const;
 
     void computeAsQuadError(SkVector* err) const;
     bool asQuadTol(SkScalar tol) const;
 
     /**
@@ skipping 171 matching lines @@
 private:
     enum {
         kQuadCount = 8, // should handle most conics
         kPointCount = 1 + 2 * kQuadCount,
     };
     SkAutoSTMalloc<kPointCount, SkPoint> fStorage;
     int fQuadCount; // #quads for current usage
 };
 
 #endif