Add query for block dimensions of a given format

src/gpu/GrSWMaskHelper.h

Index: src/gpu/GrSWMaskHelper.h
diff --git a/src/gpu/GrSWMaskHelper.h b/src/gpu/GrSWMaskHelper.h
index 340b1a3829708dc834bff4193f820837475284c0..ad1d432ea6237183677795f2c986dc737fbde150 100644
--- a/src/gpu/GrSWMaskHelper.h
+++ b/src/gpu/GrSWMaskHelper.h
@@ -15,6 +15,7 @@
 #include "SkMatrix.h"
 #include "SkRasterClip.h"
 #include "SkRegion.h"
+#include "SkTextureCompressor.h"
 #include "SkTypes.h"
 
 class GrAutoScratchTexture;
@@ -101,6 +102,10 @@ private:
     SkDraw          fDraw;
     SkRasterClip    fRasterClip;
 
+#if GR_COMPRESS_ALPHA_MASK
+    SkTextureCompressor::Format fCompressedFormat;
+#endif
+
     // Actually sends the texture data to the GPU. This is called from
     // toTexture with the data filled in depending on the texture config.
     void sendTextureData(GrTexture *texture, const GrTextureDesc& desc,