[Effen] Move 'flex' out of CSS also.

[Effen] Move 'flex' out of CSS also.

This introduces a new kind of ContentNode similar to Style but which
instead of changing the styles that apply to the node, provides new
settings to apply to the "parentData" structure.

If you have better ideas for the class names here let me know.

Note that the layout.dart backend of this is hacky (more so than
before, even); once we have something other than the DOM and CSS to
back it, it'll get rewritten.

R=eseidel@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/1a4db2e964de8a2eba7c76c0904027150cc0c387

[eseidel, 2015-05-11 23:07:21]

eseidel@chromium.org changed reviewers:
+ eseidel@chromium.org

[eseidel, 2015-05-11 23:07:22]

lgtm

https://codereview.chromium.org/1129893006/diff/1/sky/framework/fn.dart
File sky/framework/fn.dart (right):

https://codereview.chromium.org/1129893006/diff/1/sky/framework/fn.dart#newco...
sky/framework/fn.dart:151: class ParentDataStyler extends ContentNode {
ParentDataSetter?

[Hixie, 2015-05-11 23:20:24]

Committed patchset #2 (id:20001) manually as
1a4db2e964de8a2eba7c76c0904027150cc0c387 (presubmit successful).

[jamesr, 2015-05-12 00:06:01]

jamesr@chromium.org changed reviewers:
+ jamesr@chromium.org

[jamesr, 2015-05-12 00:06:02]

I think this broke the tests:

http://build.chromium.org/p/client.mojo/console

Please use the trybots - all you have to do is type "git cl try" after uploading

[Hixie, 2015-05-12 17:20:22]

https://codereview.chromium.org/1122413006