goog.forwardDeclare is deprecated

[xvilo]

The goog.forwardDeclare function is deprecated and is actively cleaned up with goog.requireType. When building with version v20200614 (June 17th 2020), you'll get the following erros:

/closure/goog/events/eventhandler.js:55: ERROR - [JSC_MISSING_MODULE_OR_PROVIDE] Required namespace "goog.events.EventWrapper" never defined.
  55| goog.requireType('goog.events.EventWrapper');
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

/closure/goog/events/events.js:57: ERROR - [JSC_MISSING_MODULE_OR_PROVIDE] Required namespace "goog.events.EventWrapper" never defined.
  57| goog.requireType('goog.events.EventWrapper');
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

2 error(s), 0 warning(s)

Currently the last supported Google Closure Library by Plovr is v20200517 (May 19th 2020). I do not have enough knowledge about Plovr's internals to easily fix this and I hope someone can look into this.