am 3556305e: Merge "docs: hide the "back to top" link when there\'s no...

am 3556305e: Merge "docs: hide the "back to top" link when there\'s no vertical scroll also use local variables for DOM objects (in a slow effort to eventually remove all non-essential global vars)" into eclair

Merge commit '3556305e' into eclair-plus-aosp

* commit '3556305e':
  docs: hide the "back to top" link when there's no vertical scroll