Fix fast/css/font-face-woff2.html

The test failure was caused by a OTS roll including woff2 format change.
This patch updates Ahem.woff2 to the latest woff2 format, and re-enables
fast/css/font-face-woff2.html test.

Ahem.woff2 is generated from Ahem.ttf in the same directory using the
woff2_compress tool [1], with Brotli compression enabled.

[1] https://code.google.com/p/font-compression-reference/
    revision 05b3775ecbd31f3a8a4f9ff5a3afe72a926db447

BUG=357727

Review URL: https://codereview.chromium.org/218883002

git-svn-id: svn://svn.chromium.org/blink/trunk@170433 bbb929c8-8fbe-4397-9dbb-9b2b20218538