Use CTFontCreateForString for RenderTextHarfbuzz on Mac
The approach ends up pretty close to what's already done for Windows.
On Mac, CTFontCreateForString() gives better fallbacks (i.e. they more
often match what native UI does) and requires RenderTextHarfbuzz to do
less work. However, it doesn't guarantee that the returned font can
display every glyph in the provided string.
So still use CTFontCopyDefaultCascadeListForLanguages (which is now a
public API - hooray) to provide a last-resort list of fallback fonts.
BUG=696867, 619684
Review-Url: https://codereview.chromium.org/2927953003
Cr-Commit-Position: refs/heads/master@{#481062}
6 files changed
