function getRawEventName(topLevelType) {
  return unsafeCastDOMTopLevelTypeToString(topLevelType);
}
To identify top level events in ReactDOM, we use constants defined by this
module. This is the only module that uses the unsafe* methods to express
that the constants actually correspond to the browser event names. This lets
us save some bundle size by avoiding a top level type -> event name map.
The rest of ReactDOM code should import top level types from this file.