Add a PNGEncoder helper function that takes an SkBitmap,

base/gfx/png_encoder.cc

 // Copyright (c) 2006-2008 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/basictypes.h"
 #include "base/gfx/png_encoder.h"
 #include "base/logging.h"
+#include "skia/include/SkBitmap.h"
 
 extern "C" {
 #include "png.h"
 }
 
 namespace {
 
 // Converts BGRA->RGBA and RGBA->BGRA.
 void ConvertBetweenBGRAandRGBA(const unsigned char* input, int pixel_width,
                                unsigned char* output) {
@@ skipping 166 matching lines @@
       converter(&input[y * row_byte_width], w, row);
       png_write_row(png_ptr, row);
     }
     delete[] row;
   }
 
   png_write_end(png_ptr, info_ptr);
   return true;
 }
 
+// static
+bool PNGEncoder::EncodeBGRASkBitmap(const SkBitmap& input,
+                                    bool discard_transparency,
+                                    std::vector<unsigned char>* output) {
+  SkAutoLockPixels input_lock(input);
+  DCHECK_EQ(input.bytesPerPixel(), 4);
+  return Encode(static_cast<unsigned char*>(input.getPixels()),
+                PNGEncoder::FORMAT_BGRA, input.width(), input.height(),
+                input.rowBytes(), discard_transparency, output);
+}
+