Move simple png encoding for image_diff into tools/

webkit/support/webkit_support_gfx.h

-// 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.
-
-#ifndef WEBKIT_SUPPORT_WEBKIT_SUPPORT_GFX_H_
-#define WEBKIT_SUPPORT_WEBKIT_SUPPORT_GFX_H_
-
-#include <string>
-#include <vector>
-
-namespace webkit_support {
-
-// Decode a PNG into an RGBA pixel array.
-bool DecodePNG(const unsigned char* input, size_t input_size,
-               std::vector<unsigned char>* output,
-               int* width, int* height);
-
-// Encode an RGBA pixel array into a PNG.
-bool EncodeRGBAPNG(const unsigned char* input,
-                   int width,
-                   int height,
-                   int row_byte_width,
-                   std::vector<unsigned char>* output);
-
-// Encode an BGRA pixel array into a PNG.
-bool EncodeBGRAPNG(const unsigned char* input,
-                   int width,
-                   int height,
-                   int row_byte_width,
-                   bool discard_transparency,
-                   std::vector<unsigned char>* output);
-
-bool EncodeBGRAPNGWithChecksum(const unsigned char* input,
-                               int width,
-                               int height,
-                               int row_byte_width,
-                               bool discard_transparency,
-                               const std::string& checksum,
-                               std::vector<unsigned char>* output);
-
-}  // namespace webkit_support
-
-#endif  // WEBKIT_SUPPORT_WEBKIT_SUPPORT_GFX_H_