Move simple png encoding for image_diff into tools/

tools/imagediff/image_diff_png.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_
+#ifndef TOOLS_IMAGEDIFF_IMAGE_DIFF_PNG_H_
+#define TOOLS_IMAGEDIFF_IMAGE_DIFF_PNG_H_
 
 #include <string>
 #include <vector>
 
-namespace webkit_support {
+namespace image_diff_png {
 
 // 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 image_diff_png
 
-}  // namespace webkit_support
-
-#endif  // WEBKIT_SUPPORT_WEBKIT_SUPPORT_GFX_H_
+#endif  // TOOLS_IMAGEDIFF_IMAGE_DIFF_PNG_H_