Fix memory leak in SkGradientShader.

src/core/SkPictureShader.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPictureShader_DEFINED
 #define SkPictureShader_DEFINED
 
@@ skipping 51 matching lines @@
 protected:
     SkPictureShader(SkReadBuffer&);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
 private:
     SkPictureShader(SkPicture*, TileMode, TileMode);
 
     SkShader* validInternal(const SkBitmap& device, const SkPaint& paint,
                             const SkMatrix& matrix, SkMatrix* totalInverse) const;
 
-    SkShader* buildBitmapShader(const SkMatrix&) const;
+    SkShader* refBitmapShader(const SkMatrix&) const;
 
     SkPicture*  fPicture;
     TileMode    fTmx, fTmy;
 
     mutable SkMutex                 fCachedBitmapShaderMutex;
     mutable SkAutoTUnref<SkShader>  fCachedBitmapShader;
     mutable SkSize                  fCachedTileScale;
     mutable SkMatrix                fCachedLocalMatrix;
 
     typedef SkShader INHERITED;
 };
 
 #endif // SkPictureShader_DEFINED