ApiExpandTemplates: Start parse before creating frame

The code added in Id12cbe4a is creating a frame from the parser object
before actually starting a parse, meaning the frame ends up with no
title, which causes problems for other stuff that assumes the frame
*does* have a title.

While we could possibly change from calling ->preprocess() to
->recursivePreprocess() to avoid re-starting the parse, there are some
hooks called from ->preprocess() that it's probably best to continue
calling to not break BC.

Bug: 66798
Change-Id: If2ca8ab94ab81ee10f33ce1f4ee75655b7c1e680
(cherry picked from commit 682c7da095132703606c29375c00b70e6ebc297f)