Update test .woff2 font file and re-enable woff2 test

The compression algorithm of WOFF 2.0 has switched from LZMA to Brotli.
This patch updates Ahem.woff2 to an "uncompressed" (pre-processing only)
woff2 format, since we expect some incompatible changes in Brotli binary
format. Also re-enables fast/css/font-face-woff2.html test.

Ahem.woff2 is generated from Ahem.ttf in the same directory
using font-compression-reference tool[1] with the following command:

java -cp build/jar/compression.jar \
  com.google.typography.font.compression.CompressionRunner \
  -x glyf/cbbox,triplet,code,reslice:woff2 -o Ahem.ttf

[1] https://code.google.com/p/font-compression-reference/
    revision 5ce8fad3ab9824f9f4d5fb4768c313b6309e94e3

BUG=307828

Review URL: https://codereview.chromium.org/117313004

git-svn-id: svn://svn.chromium.org/blink/trunk@164068 bbb929c8-8fbe-4397-9dbb-9b2b20218538