Add performance test of character_fallback with AAT fonts

crbug.com/547912 figured out that font fallback runs different code
path for AAT fonts. This patch adds a performance test that
specifically runs the code path.

BUG=547912

Review URL: https://codereview.chromium.org/1578913003

Cr-Commit-Position: refs/heads/master@{#372636}
2 files changed