Initial implementation of SnackBar

Initial implementation of SnackBar

R=abarth@chromium.org, abarth@google.com

Committed: https://chromium.googlesource.com/external/mojo/+/517bc68ed4e691a055826cc478a1a5cef72fbe66

[abarth-chromium, 2015-07-06 15:16:44]

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

[abarth-chromium, 2015-07-06 15:16:45]

lgtm

https://codereview.chromium.org/1216613004/diff/1/sky/sdk/lib/widgets/snack_b...
File sky/sdk/lib/widgets/snack_bar.dart (right):

https://codereview.chromium.org/1216613004/diff/1/sky/sdk/lib/widgets/snack_b...
sky/sdk/lib/widgets/snack_bar.dart:27: }
We should probably remove this function.  |label| and |onPressed| are final, so
this function will throw if called.  Fortuantely, SnackBarAction isn't stateful,
so this function never gets called.

https://codereview.chromium.org/1216613004/diff/1/sky/sdk/lib/widgets/snack_b...
sky/sdk/lib/widgets/snack_bar.dart:58: }
ditto

https://codereview.chromium.org/1216613004/diff/1/sky/sdk/lib/widgets/snack_b...
sky/sdk/lib/widgets/snack_bar.dart:77: margin: const
EdgeDims.symmetric(horizontal: 24.0),
Why margin rather than padding?  I guess it does't matter since this container
does't have a background color.

[jackson, 2015-07-06 15:30:58]

https://codereview.chromium.org/1216613004/diff/1/sky/sdk/lib/widgets/snack_b...
File sky/sdk/lib/widgets/snack_bar.dart (right):

https://codereview.chromium.org/1216613004/diff/1/sky/sdk/lib/widgets/snack_b...
sky/sdk/lib/widgets/snack_bar.dart:27: }
On 2015/07/06 15:16:45, abarth-chromium wrote:
> We should probably remove this function.  |label| and |onPressed| are final,
so
> this function will throw if called.  Fortuantely, SnackBarAction isn't
stateful,
> so this function never gets called.

Agree, but as we discussed, we should probably have stateful components inherit
from StatefulComponent rather than passing a boolean to super so you can't
forget to implement this function when you start adding state to a component and
you'll get an analyzer warning when you try to call super.syncFields on a
stateless component. I will investigate.

https://codereview.chromium.org/1216613004/diff/1/sky/sdk/lib/widgets/snack_b...
sky/sdk/lib/widgets/snack_bar.dart:77: margin: const
EdgeDims.symmetric(horizontal: 24.0),
On 2015/07/06 15:16:45, abarth-chromium wrote:
> Why margin rather than padding?  I guess it does't matter since this container
> does't have a background color.

Yeah.

[jackson, 2015-07-06 15:40:40]

Committed patchset #2 (id:20001) manually as
517bc68ed4e691a055826cc478a1a5cef72fbe66 (presubmit successful).