add new readPixels with direct memory parameters

tools/sk_tool_utils.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef sk_tool_utils_DEFINED
 #define sk_tool_utils_DEFINED
 
 #include "SkCanvas.h"
 #include "SkBitmap.h"
 
 namespace sk_tool_utils {
+    
+    const char* colortype_name(SkColorType);
 
     /**
      *  Return the colorType and alphaType that correspond to the specified Config8888
      */
     void config8888_to_imagetypes(SkCanvas::Config8888, SkColorType*, SkAlphaType*);
 
     /**
      *  Call canvas->writePixels() by using the pixels from bitmap, but with an info that claims
      *  the pixels are colorType + alphaType
      */
     void write_pixels(SkCanvas*, const SkBitmap&, int x, int y, SkColorType, SkAlphaType);
 }
 
 #endif