Set up some hooks for premul/swizzzle opts.

src/core/SkOpts.h

Index: src/core/SkOpts.h
diff --git a/src/core/SkOpts.h b/src/core/SkOpts.h
index 1b94126cf724bff8d233e8dc305a80d95fa79e5b..85e38fe13969b43de2d378e22685747e25efa83d 100644
--- a/src/core/SkOpts.h
+++ b/src/core/SkOpts.h
@@ -57,6 +57,11 @@ namespace SkOpts {
                                           const SkColor*);
 
     extern SkMatrix::MapPtsProc matrix_translate, matrix_scale_translate, matrix_affine;
+
+    typedef void (*Swizzle_8888_8888)(uint32_t[], const uint32_t[], int);
+    extern Swizzle_8888_8888 premul_xxxa,  // BGRA -> bgrA or RGBA -> rgbA
+                             swaprb_xxxa,  // BGRA -> RGBA or RGBA -> BGRA
+                      premul_swaprb_xxxa;  // BGRA -> rgbA or RGBA -> bgrA
 }
 
 #endif//SkOpts_DEFINED