Added kSRGBLinear_Named color space, along with tests

include/core/SkColorSpace.h

Index: include/core/SkColorSpace.h
diff --git a/include/core/SkColorSpace.h b/include/core/SkColorSpace.h
index b2b005e4aa6b8c2e6e82b4f36474a5daec68dea9..24bce488751dfd9420916f13926eec8269dd8afa 100644
--- a/include/core/SkColorSpace.h
+++ b/include/core/SkColorSpace.h
@@ -31,6 +31,11 @@ public:
          *  Often used by images and monitors.
          */
         kAdobeRGB_Named,
+
+        /**
+         * Colorspace with the sRGB primaries, but a linear (1.0) gamma.

[msarett, 2016/09/27 20:53:52]

Might be interesting to comment on why this is interesting/commonly used to
justify that it belongs here.

+         */
+        kSRGBLinear_Named,
     };
 
     enum RenderTargetGamma : uint8_t {