ash_unittests --mash --gtest_filter=PartialMagnificationControllerTest.*

4 tests failed:
    PartialMagnificationControllerTest.ActiveOnPointerDown (../../ash/magnifier/partial_magnification_controller_unittest.cc:70)
    PartialMagnificationControllerTest.DisablingDisablesActive (../../ash/magnifier/partial_magnification_controller_unittest.cc:110)
    PartialMagnificationControllerTest.MagnifierFollowsPointer (../../ash/magnifier/partial_magnification_controller_unittest.cc:130)
    PartialMagnificationControllerTest.MultipleDisplays (../../ash/magnifier/partial_magnification_controller_unittest.cc:91)

The "host widget" is null under mash.

Unclear if this is a magnifier problem or an EventGenerator problem.