Prevent race condition in applying CSS styles for content

Currently the CSS styles intended for talk page content are
occassionally getting applied to regular page content due to a
race condition. This prevents the talk page styles from ever
accidently being applied elsewhere.

Change-Id: I50d9b44a18b68c2d5f040f49b162e92167b76d33
Merge "Prevent race condition in applying CSS styles for content"