[mdv] implement Node.createBinding and Node.createBindings

[mdv] implement Node.createBinding and Node.createBindings
port of
https://github.com/Polymer/mdv/commit/95c4eca5a89ed3d04af1c6607a61f49d35d05ca6, https://github.com/Polymer/mdv/commit/3a0d2f302d474cd175d7fe49b278f928a019d053

BUG=
R=sigmund@google.com

Committed: https://code.google.com/p/dart/source/detail?r=25485

[Jennifer Messerly, 2013-07-25 00:02:52]

more progress to catching up with MDV

[Siggi Cherem (dart-lang), 2013-07-25 16:24:12]

lgtm!

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/element.dart
File pkg/mdv/lib/src/element.dart (right):

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/element.da...
pkg/mdv/lib/src/element.dart:45: node.xtag.attributes[property] =
sanitizeBoundValue(value);
should that escaping be defined in sanitizeBoundValue? (maybe override
sanitizeBoundValue here in AttributeBinding?

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/input_bind...
File pkg/mdv/lib/src/input_bindings.dart (right):

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/input_bind...
pkg/mdv/lib/src/input_bindings.dart:60: get node => super.node;
remove this getter or the 'as dynamic' below?

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/node.dart
File pkg/mdv/lib/src/node.dart (right):

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/node.dart#...
pkg/mdv/lib/src/node.dart:80: * The bound data model.
silly nit: this fits in 1 line (/** ... */)

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/template_i...
File pkg/mdv/lib/src/template_iterator.dart (right):

https://codereview.chromium.org/20149004/diff/1001/pkg/mdv/lib/src/template_i...
pkg/mdv/lib/src/template_iterator.dart:242: _sub = (iteratedValue as
Observable).changes.listen(_handleChanges);
How crazy would it be to add as a language feature that we use 'is' checks to
infer the type sensitively in a block of code? I know the editor already uses it
for 'var', but I wonder if it can be used more generally:

T x;
x.foo; // warning: foo not in T
if (x is V) {
  x.foo; // ok: foo is defined in V
}

[Jennifer Messerly, 2013-07-25 18:01:14]

Committed patchset #2 manually as r25485 (presubmit successful).