Add a hook for CPU-optimized sRGB-sRGB srcover.

src/core/SkOpts.cpp

Index: src/core/SkOpts.cpp
diff --git a/src/core/SkOpts.cpp b/src/core/SkOpts.cpp
index f854033316c8eff92da47f0c5b3ecca0a8c88262..54463b250cfbbf3a5e44100e3cdf7e31897f885b 100644
--- a/src/core/SkOpts.cpp
+++ b/src/core/SkOpts.cpp
@@ -11,6 +11,7 @@
 #include "SkOpts.h"
 
 #define SK_OPTS_NS sk_default
+#include "SkBlend_opts.h"
 #include "SkBlitMask_opts.h"
 #include "SkBlitRow_opts.h"
 #include "SkBlurImageFilter_opts.h"
@@ -73,6 +74,8 @@ namespace SkOpts {
     decltype(half_to_float) half_to_float = sk_default::half_to_float;
     decltype(float_to_half) float_to_half = sk_default::float_to_half;
 
+    decltype(srcover_srgb_srgb) srcover_srgb_srgb = sk_default::srcover_srgb_srgb;
+
     // Each Init_foo() is defined in src/opts/SkOpts_foo.cpp.
     void Init_ssse3();
     void Init_sse41();