Linux: use xheight from OS2 table if given.
Linux: use xheight from OS2 table if given.

The x-height isn't really any longer the actual height of an 'x'. Some
faces provide an explicit x-height value in the OS/2 table which we
should use if given.

Review URL: http://codereview.chromium.org/12953


git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@6379 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser