fix two bugs in site script.

1. Fix URL path check for reference docs to initalize api level and sidenav.
Previously, this condition was never true, so the sidenav would not be initialized
under default conditions and the reference drag bar would not appear.
2. Fix the recent change to the 'scroll into view' script so that it works
properly in a multi-pane sidenav (reference docs) by again making the offset
measurement relative to the parent container (but much better than was done before).

Change-Id: I2a31ed59d772346651c2432f0ed26530983c49ff