NavBar: Don't resize in portrait docks when HDMI connected.

The computation moving the navbar up is too drastic when a device locked
in a portrait dock is connected to a landscape external display (e.g. a TV).
Instead, only do this if the aspect ratios of the device and external display
are the same.

Bug: 6513219
Change-Id: I7cfb1096b7d1a774032d22c4b0d7eb3177766c58