Enable sRGB on iOS, make sRGB decode support optional

tools/gpu/GrContextFactory.cpp

Index: tools/gpu/GrContextFactory.cpp
diff --git a/tools/gpu/GrContextFactory.cpp b/tools/gpu/GrContextFactory.cpp
index ffc5295ab263ecfe264347fc129932c166f59c95..8d9bd41245b67a7f920c78bca0ad5ff43d189202 100644
--- a/tools/gpu/GrContextFactory.cpp
+++ b/tools/gpu/GrContextFactory.cpp
@@ -198,6 +198,8 @@ ContextInfo GrContextFactory::getContextInfo(ContextType type, ContextOptions op
     if (ContextOptions::kUseInstanced & options) {
         grOptions.fEnableInstancedRendering = true;
     }
+    grOptions.fRequireDecodeDisableForSRGB =
+        SkToBool(ContextOptions::kRequireSRGBDecodeDisableSupport & options);
     grCtx.reset(GrContext::Create(backend, backendContext, grOptions));
     if (!grCtx.get()) {
         return ContextInfo();