Reland: Initiate webfont download right after style recalc

This patch relands https://codereview.chromium.org/63713002/
which caused timeouts on layout tests.
The problem that caused the timeouts has been fixed in
https://codereview.chromium.org/75983002/.

BUG=246492
TEST=Covered by existing tests

Review URL: https://codereview.chromium.org/77223004

git-svn-id: svn://svn.chromium.org/blink/trunk@162391 bbb929c8-8fbe-4397-9dbb-9b2b20218538