Remove StyleResolver::initializeFontStyle as a first step towards cleaning up StyleResolver's font handling

There were two callers to this function.  It turned out that one of them was dead code.

I inlined initializeFontStyle into the remaining caller (defaultStyleForElement()) in preparation
for cleaning up that method's use of StyleResolverState further.

I tried to agressively ASSERT that the !settings codepath in defaultStyleForElement() was dead
code, but it turns out it isn't quite yet.

BUG=237268
R=jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/19235006

git-svn-id: svn://svn.chromium.org/blink/trunk@154353 bbb929c8-8fbe-4397-9dbb-9b2b20218538