Move styles.less to index.less and import print.less from it. This keeps
the reasoning about styles constrained to LESS instead of spread out
over LESS _and_ ResourceLoader. The former is preferable since LESS is
more standardized than ResourceLoader.
The approach of moving styles.less to index.less and then referencing
print.less was chosen with the intent that it'd be easier to assume
styles are screen styles unless a media query says otherwise.
This patch also makes the variables import common among print and screen
styles.
Bug: T246419
Change-Id: I981d0937aaacb7cba082c337f98c90e90b46b340
ac069fbec1