Use mw-ui classes instead of flow-ui

Corrects subscription icon appearing the wrong color.
Depends on mw-ui-anchor patch to land in Core,
but can be landed independently.

Change-Id: I5fe68ba1fc263278ce92707f7c83ee3f616ba3a2
Dependency: I89d80927d603407678182592a1b12e2132de4141
Merge "Use mw-ui classes instead of flow-ui"