Currently, RepostFormTabHelper::PresentDialog() takes a location from which to present the form resubmission dialog on iPad.  This location is then passed to the delegate to present the dialog.   Issue 901885  occurred because the location is given in the wrong coordinate space.  crrev.com/c/1379036 updates the logic so that RepostFormCoordinator takes CGPoints in its baseViewController's coordinate space.  However, this is still not the best solution because it requires BVC to know that it's being used as the RepostFormCoordinator.baseViewController.

The origin point calculation should occur in BrowserCoordinator so that BVC no longer has to make assumptions that the RepostFormTabHelperDelegate implementation sets up an alert in its coordinate space.