Merge changes from topic "caitlinshk-dock-defend-initial" into tm-qpr-dev

* changes:
  [Dock Defend] Cache the density in the drawable so we don't re-fetch it constantly.
  [Dock Defend] Udpate the content description to account for dock defend if needed.
  [Battery] Ensure we always update the text and content description when necessary.
  [Dock Defend] Ensure the bottom of the battery icon is always aligned with the bottom of the other icons, even if the shield is displayed.
  [Dock Defend] Add an optional shield to the status bar battery drawable.