Add preliminary ASTC encoder

src/utils/SkTextureCompressor.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 SkTextureCompressor_DEFINED
 #define SkTextureCompressor_DEFINED
 
 #include "SkImageInfo.h"
 #include "SkBlitter.h"
 
 class SkBitmap;
 class SkData;
 
 namespace SkTextureCompressor {
     // Various texture compression formats that we support.
     enum Format {
         // Alpha only formats.
-        kLATC_Format,    // 4x4 blocks, compresses A8
-        kR11_EAC_Format, // 4x4 blocks, compresses A8
+        kLATC_Format,       // 4x4 blocks, compresses A8
+        kR11_EAC_Format,    // 4x4 blocks, compresses A8
+        kASTC_12x12_Format, // 12x12 blocks, compresses A8
 
-        kLast_Format = kR11_EAC_Format
+        kLast_Format = kASTC_12x12_Format
     };
     static const int kFormatCnt = kLast_Format + 1;
 
     // Returns the size of the compressed data given the width, height, and
     // desired compression format. If the width and height are not an appropriate
     // multiple of the block size, then this function returns an error (-1).
     int GetCompressedDataSize(Format fmt, int width, int height);
 
     // Returns an SkData holding a blob of compressed data that corresponds
     // to the bitmap. If the bitmap colorType cannot be compressed using the 
@@ skipping 15 matching lines @@
                                     int width, int height, int rowBytes);
 
     // Returns the blitter for the given compression format. Note, the blitter
     // is intended to be used with the proper input. I.e. if you try to blit
     // RGB source data into an R11 EAC texture, you're gonna have a bad time.
     SkBlitter* CreateBlitterForFormat(int width, int height, void* compressedBuffer,
                                       Format format);
 }
 
 #endif