Update DisplayMetrics even on default display

Fix a bug where the DisplayMetrics wouldn't be updated for a Resources
object on the default display. Since multi-window, we want to update
all Resources.

This didn't always manifest itself due to recreation of assets, which
would force an update of DisplayMetrics. Re-use of an AssetManager from
the cache would expose the bug.

Bug:32133693
Bug:31998629
Test: cts-tradefed run cts --module CtsServicesHostTestCases
Change-Id: Ic51ab82710517b87eb995ccf982085dba876ad58