Fix for Issue 331895: Make gesturenav screenshot greyscale

ui/gfx/codec/png_codec.h

 // Copyright (c) 2011 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 UI_GFX_CODEC_PNG_CODEC_H_
 #define UI_GFX_CODEC_PNG_CODEC_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 19 matching lines @@
     // This is the native JPEG format.
     FORMAT_RGB,
 
     // 4 bytes per pixel, in RGBA order in memory regardless of endianness.
     FORMAT_RGBA,
 
     // 4 bytes per pixel, in BGRA order in memory regardless of endianness.
     // This is the default Windows DIB order.
     FORMAT_BGRA,
 
-    // 4 bytes per pixel, in pre-multiplied kARGB_8888_Config format. For use
-    // with directly writing to a skia bitmap.
+    // SkBitmap format. For Encode() kARGB_8888_Config (4 bytes per pixel) and
+    // kA8_Config (1 byte per pixel) formats are supported. kA8_Config gets
+    // encoded into a grayscale PNG treating alpha as the color intensity.
+    // For Decode() kARGB_8888_Config is always used.
     FORMAT_SkBitmap
   };
 
   // Represents a comment in the tEXt ancillary chunk of the png.
   struct GFX_EXPORT Comment {
     Comment(const std::string& k, const std::string& t);
     ~Comment();
 
     std::string key;
     std::string text;
@@ skipping 18 matching lines @@
   // comments: comments to be written in the png's metadata.
   static bool Encode(const unsigned char* input,
                      ColorFormat format,
                      const Size& size,
                      int row_byte_width,
                      bool discard_transparency,
                      const std::vector<Comment>& comments,
                      std::vector<unsigned char>* output);
 
   // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
-  // to be BGRA, 32 bits per pixel. The params |discard_transparency| and
-  // |output| are passed directly to Encode; refer to Encode for more
-  // information. During the call, an SkAutoLockPixels lock is held on |input|.
+  // to be kARGB_8888_Config, 32 bits per pixel. The params
+  // |discard_transparency| and |output| are passed directly to Encode; refer to
+  // Encode for more information. During the call, an SkAutoLockPixels lock
+  // is held on |input|.
   static bool EncodeBGRASkBitmap(const SkBitmap& input,
                                  bool discard_transparency,
                                  std::vector<unsigned char>* output);
 
   // Call PNGCodec::Encode on the supplied SkBitmap |input|. The difference
   // between this and the previous method is that this restricts compression to
   // zlib q1, which is just rle encoding.
   static bool FastEncodeBGRASkBitmap(const SkBitmap& input,
                                      bool discard_transparency,
                                      std::vector<unsigned char>* output);
 
+  // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
+  // to be kA8_Config, 8 bits per pixel. The bitmap is encoded as a grayscale
+  // PNG with alpha used for color intensity. The |output| param is passed
+  // directly to Encode; refer to Encode for more information. During the call,
+  // an SkAutoLockPixels lock is held on |input|.
+  static bool EncodeA8SkBitmap(const SkBitmap& input,
+                               std::vector<unsigned char>* output);
+
   // Decodes the PNG data contained in input of length input_size. The
   // decoded data will be placed in *output with the dimensions in *w and *h
   // on success (returns true). This data will be written in the 'format'
   // format. On failure, the values of these output variables are undefined.
   //
   // This function may not support all PNG types, and it hasn't been tested
   // with a large number of images, so assume a new format may not work. It's
   // really designed to be able to read in something written by Encode() above.
   static bool Decode(const unsigned char* input, size_t input_size,
                      ColorFormat format, std::vector<unsigned char>* output,
@@ skipping 10 matching lines @@
   static bool Decode(const unsigned char* input, size_t input_size,
                      SkBitmap* bitmap);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PNGCodec);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_CODEC_PNG_CODEC_H_