Start the process of choosing the correct compression format

src/gpu/GrSWMaskHelper.h

Index: src/gpu/GrSWMaskHelper.h
diff --git a/src/gpu/GrSWMaskHelper.h b/src/gpu/GrSWMaskHelper.h
index ad1d432ea6237183677795f2c986dc737fbde150..4c06786280a4b11087ef669fbd56072dc27d384d 100644
--- a/src/gpu/GrSWMaskHelper.h
+++ b/src/gpu/GrSWMaskHelper.h
@@ -42,7 +42,7 @@ class GrDrawTarget;
 class GrSWMaskHelper : SkNoncopyable {
 public:
     GrSWMaskHelper(GrContext* context)
-    : fContext(context) {
+    : fContext(context), fCompressMask(false) {
     }
 
     // set up the internal state in preparation for draws. Since many masks
@@ -102,9 +102,13 @@ private:
     SkDraw          fDraw;
     SkRasterClip    fRasterClip;
 
-#if GR_COMPRESS_ALPHA_MASK
+    // This flag says whether or not we should compress the mask. If
+    // it is true, then fCompressedFormat is always valid.
+    bool                        fCompressMask;
+
+    // This is the desired format within which to compress the
+    // texture. This value is only valid if fCompressMask is true.
     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.