Settings menu item in stock2 doesn't work

Settings menu item in stock2 doesn't work

The underlying problem is that we lacked a RenderObjectWrapper for the
RenderView, which meant we couldn't handle changing the RenderObject that was
the root of the RenderView. This CL introduces a RenderViewWrapper and uses it
in a new AppContainer widget root. This change allows us to make App a
non-magical Component that is inserted into the AppContainer in the newly
introduced runApp function.

R=ianh@google.com

Committed: https://chromium.googlesource.com/external/mojo/+/6f8f7587ae8e6f0f30f45f4d8848087794f50c3e

[Hixie, 2015-06-17 19:21:25]

lgtm

https://codereview.chromium.org/1184823006/diff/1/sky/sdk/lib/app/view.dart
File sky/sdk/lib/app/view.dart (right):

https://codereview.chromium.org/1184823006/diff/1/sky/sdk/lib/app/view.dart#n...
sky/sdk/lib/app/view.dart:45: RenderView get renderView => _renderView;
I had specifically not made that visible because I don't want people setting the
child directly, rather than through our 'root' setter below. Should we remove
the root setter and have people set it on the renderView directly?

https://codereview.chromium.org/1184823006/diff/1/sky/sdk/lib/widgets/widget....
File sky/sdk/lib/widgets/widget.dart (right):

https://codereview.chromium.org/1184823006/diff/1/sky/sdk/lib/widgets/widget....
sky/sdk/lib/widgets/widget.dart:477: assert(parent != null || this is
RenderViewWrapper);
This should never be called for RenderViewWrapper. It does tons of work that's
irrelevant for that class. We should just override it in RenderViewWrapper to do
the one line of code we care about (_root = createNode()), and in fact, maybe
should even fix that.

In fact, maybe we should refactor RenderObjectWrapper into two, so that
RenderViewWrapper can inherit from a version of it that doesn't use
createNode().

[abarth-chromium, 2015-06-17 19:37:03]

Committed patchset #1 (id:1) manually as
6f8f7587ae8e6f0f30f45f4d8848087794f50c3e (presubmit successful).