Fix scaffold to work for the toolbar.

Fix scaffold to work for the toolbar.

Also, make the scaffold code more generic (with slots in a map,
instead of dedicated members for each slot).

This may eventually benefit from being split into a general
"multislot" superclass and a scaffold-specific subclass, but for now
it'll do.

R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/0d459fcef027f2457f086ebd97728b300e5b6d6c

[Hixie, 2015-06-03 20:35:46]

Note that this depends on some changes I have to Point and Rect that are in
another CL, but I'm waiting for Matt to land his changes before I upload that
one.

[abarth-chromium, 2015-06-03 20:42:03]

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

[abarth-chromium, 2015-06-03 20:42:04]

LGTM

https://codereview.chromium.org/1152163007/diff/1/sky/sdk/lib/framework/compo...
File sky/sdk/lib/framework/components2/scaffold.dart (right):

https://codereview.chromium.org/1152163007/diff/1/sky/sdk/lib/framework/compo...
sky/sdk/lib/framework/components2/scaffold.dart:179:
syncChild(floatingActionButton, old is Scaffold ? old.floatingActionButton :
null, ScaffoldSlots.FloatingActionButton);
This should be a loop of some sort.

[Hixie, 2015-06-03 20:50:49]

On 2015/06/03 at 20:42:04, abarth wrote:
> LGTM
> 
>
https://codereview.chromium.org/1152163007/diff/1/sky/sdk/lib/framework/compo...
> File sky/sdk/lib/framework/components2/scaffold.dart (right):
> 
>
https://codereview.chromium.org/1152163007/diff/1/sky/sdk/lib/framework/compo...
> sky/sdk/lib/framework/components2/scaffold.dart:179:
syncChild(floatingActionButton, old is Scaffold ? old.floatingActionButton :
null, ScaffoldSlots.FloatingActionButton);
> This should be a loop of some sort.

This is in the RenderNodeWrapper, so there's nothing to loop over, really.
I could put slots here too but that seems like a poor choice.

[Hixie, 2015-06-03 21:50:37]

Committed patchset #3 (id:40001) manually as
0d459fcef027f2457f086ebd97728b300e5b6d6c (presubmit successful).