Generalize mask helper a bit for compression

src/gpu/GrSWMaskHelper.h

Index: src/gpu/GrSWMaskHelper.h
diff --git a/src/gpu/GrSWMaskHelper.h b/src/gpu/GrSWMaskHelper.h
index 0ffaa649822726021cadd44d2dc148eead9070ec..340b1a3829708dc834bff4193f820837475284c0 100644
--- a/src/gpu/GrSWMaskHelper.h
+++ b/src/gpu/GrSWMaskHelper.h
@@ -106,6 +106,10 @@ private:
     void sendTextureData(GrTexture *texture, const GrTextureDesc& desc,
                          const void *data, int rowbytes);
 
+    // Compresses the bitmap stored in fBM and sends the compressed data
+    // to the GPU to be stored in 'texture' using sendTextureData.
+    void compressTextureData(GrTexture *texture, const GrTextureDesc& desc);
+
     typedef SkNoncopyable INHERITED;
 };