miguely 025f75b4cf Generalizes all test logic to abstract the position of the BackLayer.
Adds concrete tests for Start, Top and Bottom backlayers.

Note: EndBackLayerLayoutTest has not been added in this CL because it is
failing over layout issues. These issues are not related directly to the core
functionality of the BackLayerLayout, but it still has to be fixed. Punting
this to a separate CL.
PiperOrigin-RevId: 161667143
2017-09-21 11:29:43 -04:00
..