Move ReadFileToString to the base namespace.

cc/test/pixel_test_utils.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/test/pixel_test_utils.h"
 
 #include <string>
 #include <vector>
 
 #include "base/file_util.h"
@@ skipping 13 matching lines @@
     char* data = reinterpret_cast<char*>(&png_data[0]);
     int size = static_cast<int>(png_data.size());
     return file_util::WriteFile(file_path, data, size) == size;
   }
   return false;
 }
 
 bool ReadPNGFile(const base::FilePath& file_path, SkBitmap* bitmap) {
   DCHECK(bitmap);
   std::string png_data;
-  return file_util::ReadFileToString(file_path, &png_data) &&
+  return base::ReadFileToString(file_path, &png_data) &&
          gfx::PNGCodec::Decode(reinterpret_cast<unsigned char*>(&png_data[0]),
                                png_data.length(),
                                bitmap);
 }
 
 bool MatchesPNGFile(const SkBitmap& gen_bmp, base::FilePath ref_img_path,
                     const PixelComparator& comparator) {
   SkBitmap ref_bmp;
   if (!ReadPNGFile(ref_img_path, &ref_bmp)) {
     LOG(ERROR) << "Cannot read reference image: " << ref_img_path.value();
@@ skipping 12 matching lines @@
   }
 
   // Shortcut for empty images. They are always equal.
   if (gen_bmp.width() == 0 || gen_bmp.height() == 0)
     return true;
 
   return comparator.Compare(gen_bmp, ref_bmp);
 }
 
 }  // namespace cc