Move font unique name lookup table construction to own singleton class

Preparation for background scheduling of font unique name table
construction at browser startup. In a forthcoming CL, threading
primitives are added to support scheduling the font lookup table
construction at startup. For now, move the existing code to a separate
singleton class.

Bug: 889864
Change-Id: Idaa0bdf4cd7128e42cdc36d409eab37ae83c1d1a
Reviewed-on: https://chromium-review.googlesource.com/c/1458186
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630099}
8 files changed