Mac-ify the app-based extensions folder name.
Mac-ify the app-based extensions folder name.

BUG=http://crbug.com/16484
TEST=ensure no "extensions" folder is created as a sibling of the app binary

Review URL: http://codereview.chromium.org/155425

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@20525 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