store SkAlphaType inside SkBitmap, on road to support unpremul

src/image/SkImagePriv.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 SkImagePriv_DEFINED
 #define SkImagePriv_DEFINED
 
 #include "SkBitmap.h"
 #include "SkImage.h"
 
 class SkPicture;
 
-extern SkBitmap::Config SkImageInfoToBitmapConfig(const SkImage::Info&,
-                                                  bool* isOpaque);
+extern SkBitmap::Config SkImageInfoToBitmapConfig(const SkImage::Info&);
 
 extern int SkImageBytesPerPixel(SkImage::ColorType);
 
 extern bool SkBitmapToImageInfo(const SkBitmap&, SkImage::Info*);
 
 // Call this if you explicitly want to use/share this pixelRef in the image
 extern SkImage* SkNewImageFromPixelRef(const SkImage::Info&, SkPixelRef*,
                                        size_t rowBytes);
 
 /**
@@ skipping 37 matching lines @@
 // may be called to see if the surface and the image share the same GrTexture,
 // in which case the surface may need to perform a copy-on-write.
 extern GrTexture* SkTextureImageGetTexture(SkImage* textureImage);
 
 // Update the texture wrapped by an image created with NewTexture. This
 // is called when a surface and image share the same GrTexture and the
 // surface needs to perform a copy-on-write
 extern void SkTextureImageSetTexture(SkImage* image, GrTexture* texture);
 
 #endif