Test fails with Roboto-Regular.ttf

When the CMap tests are run against Roboto-Regular.ttf from fuchsia/garnet/bin/fonts/third_party fails with the following message:

~~~
---- font::tests::test_cmap_format_4 stdout ----
thread 'font::tests::test_cmap_format_4' panicked at 'assertion failed: `(left == right)`
  left: `37`,
 right: `36`', src/font.rs:1073:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.
~~~
