This check was introduced in bug 1811195, but was added outside of the
normal opening flow, meaning that failures after this check would not be
handled properly, leading to potential assertion failures or unhandled
content process creation failures.
This patch adds a clarifying comment to ensure that we don't add checks
to the wrong place in the future, and moves the check into
`ContentParent::CreateBrowser` such that it is handled in a similar way
to other content process creation failures.
In addition, extra logic was added to ensure `mInitialized` gets set on
TryRemoteBrowserInternal failure, as new checks have been added before
the `mInitialized` check, and this seems likely to happen more in the
future.
Differential Revision: https://phabricator.services.mozilla.com/D197541
b97f115af8