Update `flutter/test/rendering` to no longer use `TestWindow`

There are currently 14 references in `flutter/test/rendering` that make use of `TestWindow` properties, these should be updated to use `TestFlutterView` and `TestPlatformDispatcher` as appropriate for the use cases.

* `view_chrome_style_test.dart` has 4 references
* `view_test.dart` has 4 references
* `viewport_test.dart` has 6 references