function getNativeBeforeInputChars(topLevelType, nativeEvent) {
	  switch (topLevelType) {
	    case 'topCompositionEnd':
	      return getDataFromCustomEvent(nativeEvent);
	    case 'topKeyPress':
	      /**
	       * If native `textInput` events are available, our goal is to make
	       * use of them. However, there is a special case: the spacebar key.
	       * In Webkit, preventing default on a spacebar `textInput` event
	       * cancels character insertion, but it *also* causes the browser
	       * to fall back to its default spacebar behavior of scrolling the
	       * page.
	       *
	       * Tracking at:
	       * https://code.google.com/p/chromium/issues/detail?id=355103
	       *
	       * To avoid this issue, use the keypress event as if no `textInput`
	       * event is available.
	       */
	      var which = nativeEvent.which;
	      if (which !== SPACEBAR_CODE) {
	        return null;
	      }

	      hasSpaceKeypress = true;
	      return SPACEBAR_CHAR;

	    case 'topTextInput':
	      // Record the characters to be added to the DOM.
	      var chars = nativeEvent.data;

	      // If it's a spacebar character, assume that we have already handled
	      // it at the keypress level and bail immediately. Android Chrome
	      // doesn't give us keycodes, so we need to blacklist it.
	      if (chars === SPACEBAR_CHAR && hasSpaceKeypress) {
	        return null;
	      }

	      return chars;

	    default:
	      // For other native event types, do nothing.
	      return null;
	  }
	}
@param {string} topLevelType Record from `EventConstants`.
@param {object} nativeEvent Native browser event.
@return {?string} The string corresponding to this `beforeInput` event.