PhantomJS HTMLElement is an object instead of a function

[Risto-Stevcev]

1. Which version of PhantomJS are you using? Tip: run phantomjs --version.
   2.1.1

2. What steps will reproduce the problem?
   typeof HTMLElement returns object instead of function

3. Which operating system are you using?
   Linux

4. Did you use binary PhantomJS or did you compile it from source?
   binary

5. Please provide any additional information below.
   PhantomJS returns object as the HTMLElement type instead of function, whereas for other browsers it's a function. The webcomponentsjs shim expects HTMLElement to be a function in order to work

[stale]

Due to our very limited maintenance capacity, we need to prioritize our development focus on other tasks. Therefore, this issue will be automatically closed (see #15395 for more details). In the future, if we see the need to attend to this issue again, then it will be reopened. Thank you for your contribution!