This change messes with anchor links. It obscures the item being linked to.
I don't see a way around it. Undoing for now.

      Fixes #4071.

      ««« original CL description
      doc css: topbar sticks to the top of large windows.
      Rationale: for large screens, the convenience of not having to scroll
      to the top of the page to do a search outweighs having less vertical
      space.
      Tested with Chrome, Firefox, Safari with various window and text sizes.

      R=adg
      CC=gobot, golang-dev
      https://golang.org/cl/6493071

      Committer: Andrew Gerrand <adg@golang.org>
      »»»

R=golang-dev, r, dsymonds
CC=golang-dev
https://golang.org/cl/6488121