[Flexiglass] Fix PhoneStatusBarViewControllerTest broken with Flexiglass

This CL fixes two issues in the broken tests:

1. windowRootView is null in the original test code. To fix this issue,
   mock WindowRootView class instead of the provider.

2. As PhoneStatusBarViewController indicates, with Flexiglass on,
   windowRootView.dispatchTouchEvent() is called instead of
   shadeViewController.handleExternalTouch. This CL changes the test
   expectations when the flag is on.

Given that PhoneStatusBarViewControllerTest has many test cases failing
with Flexiglass on, this CL turns original tests into parameterized
tests to verify with the feature flag on/off.

Bug: 416716452
Flag: EXEMPT bugfix
Change-Id: I24ab1a83e3b9f0c5419a9f882ae642551ff2d041