Revert "Update Window Extensions library APIs"

Revert submission 20478705-functional_interface

Reason for revert: DroidMonitor-triggered revert due to breakage https://android-build.googleplex.com/builds/tests/view?testResultId=TR92628441204212347, bug b/264025195.

Reverted changes: /q/submissionid:20478705-functional_interface

Tests: https://android-build.googleplex.com/builds/abtd/run/L11300000957955121
Change-Id: I9f43d52c370d95a7a8a1e50746efc56ff3403c9c