_watchForSwfFallbackContent = function() {
    var maxWait = _globalConfig.flashLoadTimeout;
    if (typeof maxWait === "number" && maxWait >= 0) {
      var pollWait = Math.min(1e3, maxWait / 10);
      var fallbackContentId = _globalConfig.swfObjectId + "_fallbackContent";
      _swfFallbackCheckInterval = _setInterval(function() {
        var el = _document.getElementById(fallbackContentId);
        if (_isElementVisible(el)) {
          _clearTimeoutsAndPolling();
          _flashState.deactivated = null;
          ZeroClipboard.emit({
            type: "error",
            name: "swf-not-found"
          });
        }
      }, pollWait);
    }
  }
Continuously poll the DOM until either:
 (a) the fallback content becomes visible, or
 (b) we receive an event from SWF (handled elsewhere)

IMPORTANT:
This is NOT a necessary check but it can result in significantly faster
detection of bad `swfPath` configuration and/or network/server issues [in
supported browsers] than waiting for the entire `flashLoadTimeout` duration
to elapse before detecting that the SWF cannot be loaded. The detection
duration can be anywhere from 10-30 times faster [in supported browsers] by
using this approach.

@returns `undefined`
@private