Function isFallbackCompositionStart

docs/external/js/react-dom.development.js:8840–8842

* Does our fallback best-guess model think this event signifies that * composition has begun? * * @param {string} topLevelType * @param {object} nativeEvent * @return {boolean}

(topLevelType, nativeEvent)

  function isFallbackCompositionStart(topLevelType, nativeEvent) {
    return topLevelType === TOP_KEY_DOWN && nativeEvent.keyCode === START_KEYCODE;
  }
  /**
   * Does our fallback mode think that this event is the end of composition?
   *