Remove various fun hacks from CSSFontSelector.

I went over various dubious callsites in CSSFontSelector and
decided we should try removing them:

* poking at ResourceFetcher with didLoadResource(0). japhet@ thinks
it's hacky and I agree with him. This code is old.
* yanking FrameLoader::checkLoadComplete chain. abarth@ says
it's bogus. With it, the "this" guard goes away as well.

I also moved the one-shot timer FontLoader. Fingers crossed, tests seem fine.

BUG=291287
R=abarth, eae, eseidel, japhet

Review URL: https://codereview.chromium.org/25399003

git-svn-id: svn://svn.chromium.org/blink/trunk@158754 bbb929c8-8fbe-4397-9dbb-9b2b20218538