make info real in SkPixelRef, and add bitmap::asImageInfo

include/core/SkImage.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImage_DEFINED
 #define SkImage_DEFINED
 
@@ skipping 23 matching lines @@
  *  other means.
  */
 class SK_API SkImage : public SkRefCnt {
 public:
     SK_DECLARE_INST_COUNT(SkImage)
 
 #ifdef SK_SUPPORT_LEGACY_COLORTYPE
     typedef SkColorType ColorType;
 
     static const SkColorType kAlpha_8_ColorType     = kAlpha_8_SkColorType;
+    static const SkColorType kARGB_4444_ColorType   = kARGB_4444_SkColorType;
     static const SkColorType kRGB_565_ColorType     = kRGB_565_SkColorType;
     static const SkColorType kRGBA_8888_ColorType   = kRGBA_8888_SkColorType;
     static const SkColorType kBGRA_8888_ColorType   = kBGRA_8888_SkColorType;
     static const SkColorType kPMColor_ColorType     = kPMColor_SkColorType;
     static const SkColorType kLastEnum_ColorType    = kLastEnum_SkColorType;
 #endif
 
 #ifdef SK_SUPPORT_LEGACY_ALPHATYPE
     typedef SkAlphaType AlphaType;
 
@@ skipping 65 matching lines @@
     const int       fWidth;
     const int       fHeight;
     const uint32_t  fUniqueID;
 
     static uint32_t NextUniqueID();
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif