Second pass at auditing UI strings for uses of 'Extension' where 'App' would also be appropriate.
Second pass at auditing UI strings for uses of 'Extension' where 'App' would also be appropriate.

BUG=61259
TEST=none

Review URL: http://codereview.chromium.org/5262007

git-svn-id: http://src.chromium.org/svn/trunk/src@67542 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: def6c9ec9320c34652078f9cbe57dae97abb6d5e
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