Return font data synchronously on memoy cache hit.

We recently switched cache hits to return data asychronously by default.
Doing so for fonts caused a performance regression on barnesandnoble.com

BUG=276963
TEST=typical_25 PLT

Review URL: https://chromiumcodereview.appspot.com/22929025

git-svn-id: svn://svn.chromium.org/blink/trunk@156584 bbb929c8-8fbe-4397-9dbb-9b2b20218538