Revert "Cache SkTypeface in FontPlatformData on Mac"

This reverts commit bc0998dd326f2ce6f32ee622f2f6eaf394ae3d5[1] due to
an assertion on OSX.

[1] https://src.chromium.org/viewvc/blink?view=rev&revision=165347

BUG=335782
TBR=leviw
NOTRY=true

Review URL: https://codereview.chromium.org/140913012

git-svn-id: svn://svn.chromium.org/blink/trunk@165352 bbb929c8-8fbe-4397-9dbb-9b2b20218538