Fix Possible Stack Overflow

While calling getJankTracker or reportAppJankStats its possible to
overflow the stack if the view has not been added to the view hierarchy.
This change checks if the view that getJankTracker is called on is also
the rootview and returns if true.

Bug: 382074138
Test: CoreAppJankTestCases:JankTrackerTest
Flag: EXEMPT bugfix.

Change-Id: I18ac27677689cdd9d1912adee3f88204a432f9e8