update dox

include/core/SkImageInfo.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageInfo_DEFINED
 #define SkImageInfo_DEFINED
 
@@ skipping 49 matching lines @@
 }
 
 static inline bool SkAlphaTypeIsValid(unsigned value) {
     return value <= kLastEnum_SkAlphaType;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
  *  Describes how to interpret the components of a pixel.
+ *
+ *  kN32_SkColorType is an alias for whichever 32bit ARGB format is the "native"
+ *  form for skia's blitters. Use this if you don't have a swizzle preference
+ *  for 32bit pixels.
  */
 enum SkColorType {
     kUnknown_SkColorType,
     kAlpha_8_SkColorType,
     kRGB_565_SkColorType,
     kARGB_4444_SkColorType,
     kRGBA_8888_SkColorType,
     kBGRA_8888_SkColorType,
     kIndex_8_SkColorType,
 
@@ skipping 159 matching lines @@
 
     bool validRowBytes(size_t rowBytes) const {
         uint64_t rb = sk_64_mul(fWidth, this->bytesPerPixel());
         return rowBytes >= rb;
     }
 
     SkDEBUGCODE(void validate() const;)
 };
 
 #endif