Verify that callers correctly set parentUsesSize if they use the child's size...

Verify that callers correctly set parentUsesSize if they use the child's size (and fix a few cases that didn't).
This introduces a bunch of code that should only run in debug builds, but we don't have #ifdefs yet.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1182933003.

examples/widgets/spinning_mixed.dart

@@ -71,12 +71,8 @@ void rotate(double timeStamp) {
   transformBox.translate(transformBox.size.width / 2.0, transformBox.size.height / 2.0);
   transformBox.rotateZ(delta);
   transformBox.translate(-transformBox.size.width / 2.0, -transformBox.size.height / 2.0);
-
-  // tester.checkFrame();
 }
 
-final bool debugDisplayList = false; // set this to true to use the test rendering logic
-
 void main() {
   // Because we're going to use UINodes, we want to initialise its
   // AppView, not use the default one. We don't really need to do
@@ -84,7 +80,7 @@ void main() {
   // it's good practice in case we happen to not have a
   // RenderObjectToUINodeAdapter in our tree at startup, or in case we
   // want a renderViewOverride.
-  UINodeAppView.initUINodeAppView(renderViewOverride: debugDisplayList ? tester : null);
+  UINodeAppView.initUINodeAppView();
 
   RenderFlex flexRoot = new RenderFlex(direction: FlexDirection.vertical);