Trying to be consistent when members are allowed to be NULL

src/core/SkLocalMatrixShader.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLocalMatrixShader.h"
 
 #ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
@@ skipping 42 matching lines @@
 
     fProxyShader->toString(str);
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif
 
 SkShader* SkShader::CreateLocalMatrixShader(SkShader* proxy, const SkMatrix& localMatrix) {
+    if (NULL == proxy) {
+        return NULL;
+    }
+
     if (localMatrix.isIdentity()) {
         return SkRef(proxy);
     }
 
     const SkMatrix* lm = &localMatrix;
 
     SkMatrix otherLocalMatrix;
     SkAutoTUnref<SkShader> otherProxy(proxy->refAsALocalMatrixShader(&otherLocalMatrix));
     if (otherProxy.get()) {
         otherLocalMatrix.preConcat(localMatrix);
         lm = &otherLocalMatrix;
         proxy = otherProxy.get();
     }
 
     return SkNEW_ARGS(SkLocalMatrixShader, (proxy, *lm));
 }