Add command buffer support for EXT_sRGB_write_control

gpu/command_buffer/service/feature_info.cc

Index: gpu/command_buffer/service/feature_info.cc
diff --git a/gpu/command_buffer/service/feature_info.cc b/gpu/command_buffer/service/feature_info.cc
index 77000c5037eee2a85806b6bb6250b366d81f2f26..baef762db9ebe83d7824e812f36c540e6f2443ba 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -599,6 +599,17 @@ void FeatureInfo::InitializeFeatures() {
         GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING_EXT);
     validators_.texture_unsized_internal_format.AddValue(GL_SRGB_EXT);
     validators_.texture_unsized_internal_format.AddValue(GL_SRGB_ALPHA_EXT);
+
+    // GL_FRAMEBUFFER_SRGB_EXT is exposed by the GLES extension
+    // GL_EXT_sRGB_write_control (which is not part of the core, even in GLES3),
+    // and the desktop extension GL_ARB_framebuffer_sRGB (part of the core in
+    // 3.0).
+    if (feature_flags_.desktop_srgb_support ||
+        extensions.Contains("GL_EXT_sRGB_write_control")) {

[Zhenyao Mo, 2016/11/30 19:31:11]

Don't does this if IsWebGLContext(). Otherwise you leak this enum to WebGL
context and you will need to go to multiple function entries points in
WebGLRenderingContext to filter out it.

[ccameron, 2016/11/30 23:59:44]

Updated to track if we support srgb framebuffers, and only add support for
write_control if we do and we aren't in a WebGL context.

+      feature_flags_.ext_srgb_write_control = true;
+      AddExtensionString("GL_EXT_sRGB_write_control");
+      validators_.capability.AddValue(GL_FRAMEBUFFER_SRGB_EXT);
+    }
   }
 
   // On desktop, GL_EXT_texture_sRGB is required regardless of GL version,