Do not parse angle if it is negative

If the Gradient angle is negative after
modding by 360, maintain the previous platform
behavior of TOP_BOTTOM oreintation instead of
attempting to wrap it

Test: Added CTS test to verify various negative
angle measurements
Bug: 142111195

Change-Id: Id9c050a9e15717bfaff331c6a37cb34cbce0f060
2 files changed