Fix a back/forward regression in gmail.

r155718 incorrectly reordered updating the url and updating the back/forward
list during a same document navigation. This reverts that change to the
ordering, ensuring we update the url first.

BUG=280189

Review URL: https://chromiumcodereview.appspot.com/23702014

git-svn-id: svn://svn.chromium.org/blink/trunk@157132 bbb929c8-8fbe-4397-9dbb-9b2b20218538