[NaCl SDK] AppEngine: Fix navigation on the demo pages.

* Back/Forward works
* Set title properly
* Highlight navbar

BUG=none
TBR=sbc@chromium.org

Review URL: https://codereview.chromium.org/69933002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234397 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234397