When the resource bundle is not available, the UI font family and the UI font size should follow the OS settings. 
When the resource bundle is not available, the UI font family and the UI font size should follow the OS settings. 

Add a guard against cases when the resource bundle is not available, which should not happen in the first place.



BUG=http://crbug.com/12309


Review URL: http://codereview.chromium.org/113916

git-svn-id: http://src.chromium.org/svn/trunk/src@17875 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 2c21ee0ffafa04b3d3d0ea2305e78aae7521fc0a
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser