Sync our custom index.css with upstream

As I learned we don't fall back to standard CSS for this file.
Hence sync three lines so we're closer to upstream again.
(No changes in upstream between 4.2 and 4.4 by the way, yay.)

Bug: 54823
Change-Id: I51be3cb4ab9a4c3feaee64348c5d71f15f287724
Merge "Sync our custom index.css with upstream"