Add _aa variants of Xfermode benches.

bench/Benchmark.h

Index: bench/Benchmark.h
diff --git a/bench/Benchmark.h b/bench/Benchmark.h
index 5ba6e9110893b442f6952dfd9711c7468d03cf24..22b52ab4e879d65d061320b49f611697c7e375cf 100644
--- a/bench/Benchmark.h
+++ b/bench/Benchmark.h
@@ -13,11 +13,10 @@
 #include "SkString.h"
 #include "SkTRegistry.h"
 
-#define DEF_BENCH(code)                                                 \
-namespace {                                                             \
-static Benchmark* SK_MACRO_APPEND_LINE(factory)(void*) { code; }      \
-BenchRegistry SK_MACRO_APPEND_LINE(g_R_)(SK_MACRO_APPEND_LINE(factory)); \
-}
+#define DEF_BENCH3(code, N) \
+    static BenchRegistry gBench##N([](void*) -> Benchmark* { code; });
+#define DEF_BENCH2(code, N) DEF_BENCH3(code, N)
+#define DEF_BENCH(code) DEF_BENCH2(code, __COUNTER__)
 
 /*
  *  With the above macros, you can register benches as follows (at the bottom