NEON optimizations for gray -> RGBA (or BGRA) conversions

bench/SwizzleBench.cpp

Index: bench/SwizzleBench.cpp
diff --git a/bench/SwizzleBench.cpp b/bench/SwizzleBench.cpp
index c78f2c977d8fd9e0738b1fca3e8bf5a7ad7f4d9f..0f85b59481669ad667ffdaa0ad466fa2201d2bbc 100644
--- a/bench/SwizzleBench.cpp
+++ b/bench/SwizzleBench.cpp
@@ -32,3 +32,4 @@ DEF_BENCH(return new SwizzleBench("SkOpts::RGBA_to_bgrA", SkOpts::RGBA_to_bgrA))
 DEF_BENCH(return new SwizzleBench("SkOpts::RGBA_to_BGRA", SkOpts::RGBA_to_BGRA));
 DEF_BENCH(return new SwizzleBench("SkOpts::RGB_to_RGB1",  SkOpts::RGB_to_RGB1));
 DEF_BENCH(return new SwizzleBench("SkOpts::RGB_to_BGR1",  SkOpts::RGB_to_BGR1));
+DEF_BENCH(return new SwizzleBench("SkOpts::gray_to_RGB1", SkOpts::gray_to_RGB1));