Focus.at() and company should be on Focus, not FocusState.
_notifyDescendants() was using the wrong runtimeType.
Let InheritedWidget update the descendants during build.
When you setState() during build, assert that you're not
markNeedsBuild()ing someone who isn't a descendant.
Typo in Widget.toString().
This patch makes a number of changes:
1) buildDirtyComponents now prevents all calls to setState, not just those
higher in the tree. This change is necessary for consistency with
MixedViewport and HomogeneousViewport because those widgets already build
subwidgets with that restriction. If the "normal" build didn't enforce that
rule, then some widgets would break when put inside a mixed or homogeneous
viewport.
2) We now notify global key listeners in a microtask after beginFrame. That
means setState is legal in these callbacks and that we'll produce another
frame if someone calls setState in such a callback.
