Add tests for NotificationGutsManager

This CL adds two tests for NotificationGutsManager:
- opening and closing guts
- Reinflate and replace guts by changing density (or font scale)

Bug: None
Test: Compiled and ran "runtest systemui"

Change-Id: Ic51fa97d18ec78a2c74dd16d01440a2e0f9991ef
4 files changed