Override type only if it's necessary

Before, WindowContext overrode type to all attached windows.
However, it led to unexpected layout when overriding an application sub panel.

This CL changes to override window type only if the type is not valid for
the attached WindowContext.

Test: atest WindowContextTest
Bug: 435160153
Flag: EXEMPT BUGFIX
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:dec18d7cffd6c57e8205716ababbb8c495fe2633
Merged-In: I161fc42386d5981b91505305110fa6214870e3e7
Change-Id: I161fc42386d5981b91505305110fa6214870e3e7