Chrome Version: (copy from chrome://version)
OS: (e.g. Win10, MacOS 10.12, etc...)

What steps will reproduce the problem?
(1) Create an extension with permissions to http://foo.bar/
    (i.e. cross-origin URLs from the extension origin),
    and from the background page create two or more
    new SharedWorker('http://foo.bar/...').

What is the expected result?
SharedWorkers are successfully loaded? (Not sure whether we should expect external SharedWorkers from background pages though)

What happens instead?
DCHECK() at
https://codesearch.chromium.org/chromium/src/content/browser/shared_worker/shared_worker_instance.cc?type=cs&g=0&l=38
fails, because the constructor origin (chrome-extension://...) and the worker's URL's origin (http://foo.bar) are different.