Reapply "add more unit tests for WorkspaceItemProcessor"

Also, add more unit tests around Widgets.

This reverts commit d9ed5f301b559873ac9b37c2c4f4245ceb82f380.

Test: Added unit tests
Flag: N/A
Bug: 330906931
Bug: 294386159

Change-Id: I8de74bce8bddd06e5ce1399d26253cb936281bee
1 file changed