Due to changes in AuraInit, chrome --mash was crashing when the ash process shutdown unexpectedly.

This lead to the following revert: https://chromium.googlesource.com/chromium/src.git/+/e3f9dbb7b50ab80caf29071bef886c2ec8cee28c

This means that when running chrome --mash, there is a ui::ResourceBundle::HasSharedInstance()

However no ash_unittests --mash caught this error. So the shared resource bundle doesn't exist there. So our test setup has drifted from the actual running.

We should find out why, and at least add a test specifically for shared resource startup.