add custom_element package

add custom_element package

code is from https://github.com/dart-lang/web-ui/blob/polymer/lib/custom_element.dart

Includes a test for the polyfill. It also includes a static analysis test to catch the common errors of forgetting to add an Element API. Because we had analysis errors in "observe" and "mdv" packages too, I added tests for them too, and fixed the issues.

R=sigmund@google.com

Committed: https://code.google.com/p/dart/source/detail?r=25591

[Jennifer Messerly, 2013-07-27 01:35:08]

https://codereview.chromium.org/20886002/diff/5001/pkg/custom_element/test/an...
File pkg/custom_element/test/analyzer_test.dart (right):

https://codereview.chromium.org/20886002/diff/5001/pkg/custom_element/test/an...
pkg/custom_element/test/analyzer_test.dart:9: // @static-clean
this is the magic annotation to catch warnings as well as errors. Thanks to
Devon Carew for clueing me in!

[Jennifer Messerly, 2013-07-27 01:57:53]

I added some APIs to make it easier to create these guys until we integrate with
dart:html, see https://code.google.com/p/dart/issues/detail?id=12089

[Siggi Cherem (dart-lang), 2013-07-29 20:18:51]

lgtm

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/pubspe...
File pkg/custom_element/pubspec.yaml (right):

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/pubspe...
pkg/custom_element/pubspec.yaml:9: # TODO(jmesserly): fix this, we should not
depend on MDV.
just checking, is this because we don't have mutation observers yet?

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
File pkg/custom_element/test/custom_element_test.dart (right):

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
pkg/custom_element/test/custom_element_test.dart:27: return new Future(() {
I prefer to use either runAsync or Timer.run to explicitly choose which kind of
asynchrony we are using (`new Future` internally uses one or the other, but I
don't know which one it is and I believe it has changed recently)

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
pkg/custom_element/test/custom_element_test.dart:30: return new Future(() {
on each of these callbacks add an expectAsync, to ensure that the test harness
waits until they get evaluated before moving to the next test.

[Jennifer Messerly, 2013-07-29 20:22:31]

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/pubspe...
File pkg/custom_element/pubspec.yaml (right):

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/pubspe...
pkg/custom_element/pubspec.yaml:9: # TODO(jmesserly): fix this, we should not
depend on MDV.
On 2013/07/29 20:18:52, Siggi Cherem (dart-lang) wrote:
> just checking, is this because we don't have mutation observers yet?

yes

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
File pkg/custom_element/test/custom_element_test.dart (right):

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
pkg/custom_element/test/custom_element_test.dart:27: return new Future(() {
On 2013/07/29 20:18:52, Siggi Cherem (dart-lang) wrote:
> I prefer to use either runAsync or Timer.run to explicitly choose which kind
of
> asynchrony we are using (`new Future` internally uses one or the other, but I
> don't know which one it is and I believe it has changed recently)

the reason to return Future is to avoid the expectAsync, see next answer :)

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
pkg/custom_element/test/custom_element_test.dart:30: return new Future(() {
On 2013/07/29 20:18:52, Siggi Cherem (dart-lang) wrote:
> on each of these callbacks add an expectAsync, to ensure that the test harness
> waits until they get evaluated before moving to the next test.

I think it does that automatically. Pete taught me this pattern IIRC.

[Siggi Cherem (dart-lang), 2013-07-29 20:28:35]

thx

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
File pkg/custom_element/test/custom_element_test.dart (right):

https://codereview.chromium.org/20886002/diff/11001/pkg/custom_element/test/c...
pkg/custom_element/test/custom_element_test.dart:30: return new Future(() {
On 2013/07/29 20:22:31, John Messerly wrote:
> On 2013/07/29 20:18:52, Siggi Cherem (dart-lang) wrote:
> > on each of these callbacks add an expectAsync, to ensure that the test
harness
> > waits until they get evaluated before moving to the next test.
> 
> I think it does that automatically. Pete taught me this pattern IIRC.

a yes, only if you return it from the test. I didn't see the return initially.

LGTM

[Jennifer Messerly, 2013-07-29 23:00:31]

Committed patchset #6 manually as r25591 (presubmit successful).