Fix AccessibilityInputFilterTest

The root cause is that we use WM#getCurrentMetrics(New API) instead of
Display#getSize in ViewConfiguration .
However, we use a stub display in AccessibilityInputFilterTest, which
don't have a corresponding DisplayContent in WMS.
Use getDisplayContentOrCreate to create a DisplayContent if it is not
yet created, and throws exception if display object is invalid.

fixes: 148823816
Test: atest AccessibilityInputFilterTest
Test: atest WindowMetricsTests

Change-Id: I36c6b020faafebbf609a46dfdeb0c9580e115e01