Implement GL_EXT_sRGB_write_control for GL.

BUG=angleproject:1547
BUG=655247

Change-Id: I3f04ddc7032e4a47eb21ff3b8586c5b47415bb64
Reviewed-on: https://chromium-review.googlesource.com/400958
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/validationES.cpp b/src/libANGLE/validationES.cpp
index 4af40ca..d261e44 100644
--- a/src/libANGLE/validationES.cpp
+++ b/src/libANGLE/validationES.cpp
@@ -162,6 +162,9 @@
         case GL_BIND_GENERATES_RESOURCE_CHROMIUM:
             return queryOnly && context->getExtensions().bindGeneratesResource;
 
+        case GL_FRAMEBUFFER_SRGB_EXT:
+            return context->getExtensions().sRGBWriteControl;
+
         default:
             return false;
     }