Add SK_IGNORE_FASTER_TEXT_FIX define for staging Skia change.

This is to stage speeding up a8 text as seen at
https://codereview.chromium.org/337603008/ .


git-svn-id: svn://svn.chromium.org/blink/trunk@177321 bbb929c8-8fbe-4397-9dbb-9b2b20218538