DM FontMgr updates

  - return nullptr for the various makeFromFoo() that we can't support,
    and tweak a few unit tests to bail out early when they do

  - create FontStyleSet and SkTypefaces once

  - abort early from FontHostStream if we can't openStream()

  - implement SkTestTypeface::onCreateFamilyNameIterator()
    with SkOTUtils::LocalizedStrings_SingleName() so FontNames passes

  - pin out-of-range glyph IDs to zero in SkTestTypeface

Change-Id: Iac53265e331fc1c5c507513af3ab299063e6610a
Reviewed-on: https://skia-review.googlesource.com/69501
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
5 files changed