Add a mechanism for command buffer to conditionally allow ES3 enums.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index f76c085eb35b97d269bc5549fb29b0996e1b7a48..28c1e0f0c2d865043ad09ccf754650e360148749 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2474,14 +2474,6 @@ bool GLES2DecoderImpl::Initialize(
     set_log_commands(true);
   }
 
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableUnsafeES3APIs) &&
-      attrib_parser.es3_context_required) {
-    // TODO(zmo): We need to implement capabilities check to ensure we can
-    // actually create ES3 contexts.
-    set_unsafe_es3_apis_enabled(true);
-  }
-
   compile_shader_always_succeeds_ =
       base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kCompileShaderAlwaysSucceeds);
@@ -2516,6 +2508,14 @@ bool GLES2DecoderImpl::Initialize(
   }
   CHECK_GL_ERROR();
 
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableUnsafeES3APIs) &&
+      attrib_parser.es3_context_required &&
+      feature_info_->IsES3Capable()) {
+    feature_info_->EnableES3Validators();
+    set_unsafe_es3_apis_enabled(true);
+  }
+
   disallowed_features_ = disallowed_features;
 
   state_.attrib_values.resize(group_->max_vertex_attribs());