Revert 228011 "[sync] Do not override user-initiated navigations..."

> [sync] Do not override user-initiated navigations when sync setup is abandoned
> 
> When the user abandons an in-progress first-time sync setup by
> navigating to another webpage, we automatically sign out the user and
> close the existing sync setup overlay. Unfortunately,
> OptionsPage.closeOverlay has the side effect of navigating back to
> chrome://settings, and this overrides the user-initiated navigation.
> 
> This patch adds code to SyncSetupOverlay to check if the sync setup page
> is being closed, and if so, to not call OptionsPage.closeOverlay.
> 
> BUG=278030,306367,306360
> TEST=Abandon first time custom sync setup by navigating away, and make
>      sure you aren't redirected to chrome://settings. Also make sure that
>      visiting a site like google.com, then going to chrome://settings/syncSetup,
>      and then hitting the back button takes you back to google.com.
>      to the sync settings page
> 
> Review URL: https://codereview.chromium.org/26667003

TBR=rsimha@chromium.org

Review URL: https://codereview.chromium.org/26840006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228201 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228201