change SkStreams to work with sk_sp<SkData> instead of SkData*

tools/skdiff_utils.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef skdiff_utils_DEFINED
 #define skdiff_utils_DEFINED
 
 #include "skdiff.h"
 
 class SkBitmap;
 class SkData;
 class SkString;
 
 /** Returns true if the two buffers passed in are both non-nullptr,
  *  have the same length, and contain exactly the same byte values.
  */
 bool are_buffers_equal(SkData* skdata1, SkData* skdata2);
 
 /** Reads the file at the given path and returns its complete contents as an
  *  SkData object (or returns nullptr on error).
  */
 sk_sp<SkData> read_file(const char* file_path);
 
 /** Decodes the fileBits into the resource.fBitmap. Returns false on failure. */
-bool get_bitmap(SkData* fileBits, DiffResource& resource, bool sizeOnly);
+bool get_bitmap(sk_sp<SkData> fileBits, DiffResource& resource, bool sizeOnly);
 
 /** Writes the bitmap as a PNG to the path specified. */
 bool write_bitmap(const SkString& path, const SkBitmap& bitmap);
 
 /** Given an image filename, returns the name of the file containing
  *  the associated difference image.
  */
 SkString filename_to_diff_filename(const SkString& filename);
 
 /** Given an image filename, returns the name of the file containing
  *  the "white" difference image.
  */
 SkString filename_to_white_filename(const SkString& filename);
 
 /** Calls compute_diff and handles the difference and white diff resources.
  *  If !outputDir.isEmpty(), writes out difference and white images.
  */
 void create_and_write_diff_image(DiffRecord* drp,
                                  DiffMetricProc dmp,
                                  const int colorThreshold,
                                  const SkString& outputDir,
                                  const SkString& filename);
 
 #endif