[chromium] Make WebContentLayer include what it uses https://bugs.webkit.org/show_bug.cgi?id=99664 Patch by Adrienne Walker <enne@chromium.org> on 2012-10-17 Reviewed by James Robinson. * chromium/public/WebContentLayer.h: git-svn-id: https://svn.webkit.org/repository/webkit/trunk/Source/Platform/chromium/public@131697 268f45cc-cd09-0410-ab3c-d52691b4dbfc