Mark fallback fonts in new Android font config parser

The new Android fonts.xml format doesn't explicitly tag fallback
fonts, or separate them from system fonts by putting them in a
separate file. We're assuming that any nameless font is a fallback
font.

Adds a unit test to track that we see as many fallback fonts as
expected when parsing a file.

BUG=chromium:400801
R=bungeman@google.com, djsollen@google.com, tomhudson@google.com

Author: tomhudson@chromium.org

Review URL: https://codereview.chromium.org/468893002
2 files changed