Add a preliminary R11 EAC compressor

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"
 
 class SkBitmap;
 class SkData;
 
 namespace SkTextureCompressor {
     // Various texture compression formats that we support.
     enum Format {
-        // Alpha only format.
+        // Alpha only formats.
         kLATC_Format,
+        kR11_EAC_Format,
 
-        kLast_Format = kLATC_Format
+        kLast_Format = kR11_EAC_Format
     };
     static const int kFormatCnt = kLast_Format + 1;
 
     // Returns an SkData holding a blob of compressed data that corresponds
     // to the bitmap. If the bitmap colorType cannot be compressed using the 
     // associated format, then we return NULL. The caller is responsible for
     // calling unref() on the returned data.
     SkData* CompressBitmapToFormat(const SkBitmap& bitmap, Format format);
 
     // Compresses the given src data into dst. The src data is assumed to be
     // large enough to hold width*height pixels. The dst data is expected to
     // be large enough to hold the compressed data according to the format.
     bool CompressBufferToFormat(uint8_t* dst, const uint8_t* src, SkColorType srcColorType,
                                 int width, int height, int rowBytes, Format format);
 }
 
 #endif