Write chrome://sync-internals DOMUI page which is like about:sync but
automatically updates on sync events.

Make about:sync{,-internals} aliases for chrome://sync-internals.

More diagnostic capabilities will be added to chrome://sync-internals
in future CLs.

BUG=69500
TEST=Manual

Review URL: http://codereview.chromium.org/6299002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71435 0039d316-1c4b-4281-b951-d872f2087c98