Initial ASTC decoder -- currently only supports 2D LDR decomrpession modes.

src/utils/SkTextureCompressor_ASTC.h

Index: src/utils/SkTextureCompressor_ASTC.h
diff --git a/src/utils/SkTextureCompressor_ASTC.h b/src/utils/SkTextureCompressor_ASTC.h
index 152fc62f16e2b1b476ad53dde8d54c184c62299d..57ba08d44028aa0339fd39c67e6df988cb1a0642 100644
--- a/src/utils/SkTextureCompressor_ASTC.h
+++ b/src/utils/SkTextureCompressor_ASTC.h
@@ -19,6 +19,9 @@ namespace SkTextureCompressor {
                                int width, int height, int rowBytes);
 
     SkBlitter* CreateASTCBlitter(int width, int height, void* outputBuffer);
+
+    void DecompressASTC(uint8_t* dst, int dstRowBytes, const uint8_t* src,
+                        int width, int height, int blockDimX, int blockDimY);
 }
 
 #endif  // SkTextureCompressor_ASTC_DEFINED