Add initial pipeline for decompressors

src/utils/SkTextureCompressor_R11EAC.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_R11EAC_DEFINED
 #define SkTextureCompressor_R11EAC_DEFINED
 
 #include "SkBlitter.h"
 
 namespace SkTextureCompressor {
 
     bool CompressA8ToR11EAC(uint8_t* dst, const uint8_t* src,
                             int width, int height, int rowBytes);
 
     SkBlitter* CreateR11EACBlitter(int width, int height, void* outputBuffer);
+
+    void DecompressR11EAC(uint8_t* dst, int dstRB, const uint8_t* src, int width, int height);
 }
 
 #endif  // SkTextureCompressor_R11EAC_DEFINED