- force the time dilation to 1.0 for the Widget tests, so that a local
change doesn't break all the tests during development.
- add missing license block to all the files.
- set ui.window.onBeginFrame to null when you use WidgetTester, so that
the engine doesn't trigger any confusing frames after our fake frames.
This makes the sync code stop if it would have to rearrange the
RenderObjects. I'll make it handle the cross-RenderObject case, as well
as the insertion-sync case, in subsequent patches.
This should handle a case like a stateful component inside a Container
inside another Container having one of those Containers removed while
still keeping that stateful component around with its state.
The problem of how to handle the Container then being reinserted is a
separate issue not handled by this patch.
