Set SK_DEFAULT_FONT_CACHE_COUNT_LIMIT=256 on windows only

Having this limit be 256 instead of the default 2k seems to hurt the page
cyclers on mac.  256 and 2048 seem the same on windows, and having the limit
be high on windows can cause more serious problems due to GDI handle limits.

R=cpu@chromium.org, cpu
TBR=reed
NOTRY=true
BUG=314387

Review URL: https://codereview.chromium.org/59883016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235268 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235268