Enforce the restriction that placeholder names can only contain caps, numbers and underscores.
Enforce the restriction that placeholder names can only contain
caps, numbers and underscores.

BUG=37254

Review URL: http://codereview.chromium.org/1527013

git-svn-id: http://src.chromium.org/svn/trunk/src@43930 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: b10738ba4e9efb80f477b0453a3c9ba6a866685a
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