Harden degenerate gradient context handling

src/effects/gradients/SkSweepGradient.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 "SkSweepGradient.h"
 
 static SkMatrix translate(SkScalar dx, SkScalar dy) {
@@ skipping 32 matching lines @@
 void SkSweepGradient::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writePoint(fCenter);
 }
 
 size_t SkSweepGradient::onContextSize(const ContextRec&) const {
     return sizeof(SweepGradientContext);
 }
 
 SkShader::Context* SkSweepGradient::onCreateContext(const ContextRec& rec, void* storage) const {
-    return new (storage) SweepGradientContext(*this, rec);
+    return CheckedCreateContext<SweepGradientContext>(storage, *this, rec);
 }
 
 SkSweepGradient::SweepGradientContext::SweepGradientContext(
         const SkSweepGradient& shader, const ContextRec& rec)
     : INHERITED(shader, rec) {}
 
 //  returns angle in a circle [0..2PI) -> [0..255]
 static unsigned SkATan2_255(float y, float x) {
     //    static const float g255Over2PI = 255 / (2 * SK_ScalarPI);
     static const float g255Over2PI = 40.584510488433314f;
@@ skipping 203 matching lines @@
     str->appendScalar(fCenter.fX);
     str->append(", ");
     str->appendScalar(fCenter.fY);
     str->append(") ");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif