(Big 41436) Make sure Revision knows page Title.

(Big 41436) Make sure Revision knows page Title.

With $wgContentHandlerUseDB, Revision needs access to the page's Title
object to determin the page's default content model. This apparently
failed in production for newly created pages (supposedly because of
some complication with database transactions or master/client setup).

This change makes WikiPage::doEditContent pass the Title object
directly to the Revision to avoid any database issues. This also
gets rid of a pointless database read.

Change-Id: I9db228c3fcda0f8dfe52be1659014a6e4b4775af