code: function checkInstrumented() {
        if (proto['__gl_wrapped__']) {
          return false;
        }
        Object.defineProperty(proto, '__gl_wrapped__', {
          'configurable': true,
          'enumerable': false,
          'value': true
        });
        contextRestoreFns.push(function() {
          delete proto['__gl_wrapped__'];
        });
        return true;
      }
docs: We do this check only for known extensions, as Firefox will return a generic 'Object' for others and that will break everything.