startNewKeyCombination(keyName, keyEventState) {
    this._ensureInitialKeyCombination();

    const newCombinationRecord =
      new KeyCombination(this.currentCombination.keysStillPressedDict());

    newCombinationRecord.addKey(keyName, keyEventState);

    this._push(newCombinationRecord);
  }
Adds a new KeyCombination to the event history.
@param {ReactKeyName} keyName - Name of the keyboard key to add to the new
       KeyCombination
@param {KeyEventState} keyEventState The state to set the key event to