Update a comment to be more verbose and explain more cases.
Update a comment to be more verbose and explain more cases.

Also removes a TODO which is no longer relevant.

BUG=NONE

Review URL: http://codereview.chromium.org/2895001

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@51833 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