Fix ReadFileToSTring failure due to '..' in the path.

chrome/test/gpu/gpu_pixel_browsertest.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 "base/command_line.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
@@ skipping 44 matching lines @@
 
 // Corner shadow size.
 const int kCornerDecorationSize = 15;
 // Side shadow size.
 const int kSideDecorationSize = 2;
 
 // Reads and decodes a PNG image to a bitmap. Returns true on success. The PNG
 // should have been encoded using |gfx::PNGCodec::Encode|.
 bool ReadPNGFile(const FilePath& file_path, SkBitmap* bitmap) {
   DCHECK(bitmap);
+  FilePath abs_path(file_path);
+  if (!file_util::AbsolutePath(&abs_path))
+    return false;
+
   std::string png_data;
-  return file_util::ReadFileToString(file_path, &png_data) &&
+  return file_util::ReadFileToString(abs_path, &png_data) &&
          gfx::PNGCodec::Decode(reinterpret_cast<unsigned char*>(&png_data[0]),
                                png_data.length(),
                                bitmap);
 }
 
 // Encodes a bitmap into a PNG and write to disk. Returns true on success. The
 // parent directory does not have to exist.
 bool WritePNGFile(const SkBitmap& bitmap, const FilePath& file_path) {
   std::vector<unsigned char> png_data;
   if (gfx::PNGCodec::EncodeBGRASkBitmap(bitmap, true, &png_data) &&
@@ skipping 513 matching lines @@
     {160, 100, 0, 0, 0}
   };
   const size_t ref_pixel_count = sizeof(ref_pixels) / sizeof(ReferencePixel);
 
   gfx::Size container_size(400, 300);
   FilePath url =
       test_data_dir().AppendASCII("pixel_canvas2d.html");
   RunPixelTest(container_size, url, ref_img_revision_update,
                ref_pixels, ref_pixel_count);
 }