Don't allow nullptr in texels array params (unless using a transfer buffer).

include/gpu/GrTextureProvider.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTextureProvider_DEFINED
 #define GrTextureProvider_DEFINED
 
@@ skipping 27 matching lines @@
      * @param srcData   Pointer to the pixel values (optional).
      * @param rowBytes  The number of bytes between rows of the texture. Zero
      *                  implies tightly packed rows. For compressed pixel configs, this
      *                  field is ignored.
      */
     GrTexture* createTexture(const GrSurfaceDesc& desc, SkBudgeted budgeted, const void* srcData,
                              size_t rowBytes);
 
     /** Shortcut for creating a texture with no initial data to upload. */
     GrTexture* createTexture(const GrSurfaceDesc& desc, SkBudgeted budgeted) {
-        return this->createTexture(desc, budgeted, NULL, 0);
+        return this->createTexture(desc, budgeted, nullptr, 0);
     }
 
     /** Assigns a unique key to the texture. The texture will be findable via this key using
         findTextureByUniqueKey(). If an existing texture has this key, it's key will be removed. */
     void assignUniqueKeyToTexture(const GrUniqueKey& key, GrTexture* texture) {
         this->assignUniqueKeyToResource(key, texture);
     }
 
     /** Finds a texture by unique key. If the texture is found it is ref'ed and returned. */
     GrTexture* findAndRefTextureByUniqueKey(const GrUniqueKey& key);
@@ skipping 106 matching lines @@
 
 private:
     GrResourceCache* fCache;
     GrGpu* fGpu;
 
     // In debug builds we guard against improper thread handling
     SkDEBUGCODE(mutable GrSingleOwner* fSingleOwner;)
 };
 
 #endif