AOD: Invert color spans for ambient display view

Fixes a bug where notifications with color spans would not show
the text properly because we inverted the background. Now we invert
the color spans the app put on the text for the ambient view.

Fixes: 35705172
Bug: 30876804
Test: receive gmail notification, observe that subject is visible on ambient display
Change-Id: I602335562346759d62d2a69a55f3ac9d1be735a9