Convert GetInputString() to GetDestinationURL().

There's no reason to convert GURL -> string16 -> GURL.

BUG=none
TEST=none
R=sky@chromium.org

Review URL: https://codereview.chromium.org/25645003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226849 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226849