Move SkGammaColorFilter to tools, limit to sRGB

Similarly, limit GrGammaEffect to sRGB (and rename it).

BUG=skia:

Change-Id: I88feef11ab7040bca2fa4c2eed71923ded87a0d0
Reviewed-on: https://skia-review.googlesource.com/7375
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/GrYUVProvider.cpp b/src/gpu/GrYUVProvider.cpp
index f3231a4..ade72a6 100644
--- a/src/gpu/GrYUVProvider.cpp
+++ b/src/gpu/GrYUVProvider.cpp
@@ -10,7 +10,7 @@
 #include "GrRenderTargetContext.h"
 #include "GrTextureProxy.h"
 #include "GrYUVProvider.h"
-#include "effects/GrGammaEffect.h"
+#include "effects/GrSRGBEffect.h"
 #include "effects/GrYUVEffect.h"
 
 #include "SkAutoMalloc.h"
@@ -149,7 +149,7 @@
         if (ctx->caps()->srgbWriteControl()) {
             paint.setDisableOutputConversionToSRGB(true);
         } else {
-            paint.addColorFragmentProcessor(GrGammaEffect::Make(2.2f));
+            paint.addColorFragmentProcessor(GrSRGBEffect::Make(GrSRGBEffect::Mode::kSRGBToLinear));
         }
     }