[WinCairo] Unreviewed Build fix.

* platform/graphics/win/FontCustomPlatformDataCairo.h:
(FontCustomPlatformData): Correct signature in header to match
required implementation.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146912 268f45cc-cd09-0410-ab3c-d52691b4dbfc