[polymer] interop with polymer-element and polymer.js

pkg/polymer/lib/src/js/shadow_dartium.js

+// Prevent polyfilled Shadow DOM in Dartium

[Siggi Cherem (dart-lang), 2014/03/06 18:18:08]

I wonder if this file should be here or in pkg/web_components/

I don't have a good ideas yet, but I wonder if we should name them similar to
each other as well. For example, instead of
 shadowdom_dartium.js & dart_support.js

we could do:
  - dartium_support.js & dart2js_support.js
  - dart_support_before.js & dart_support_after.js
  - dart_support/before.js & dart_support/after.js
  - dart_support/pre_polyfills.js & dart_support/post_polyfills.js

[Jennifer Messerly, 2014/03/06 21:05:08]

Hmmm. That's a good question. I'm not sure... it's tricky. The web_components
package is so far only about dart2js support for features that are natively
available in Dartium dart:html. This file is only to make Dartium able to
interoperate with JS code that uses Shadow DOM. Even then, it might not work
generally. But we'll test it for Polymer.js at least and try our best to keep it
working. I'm not sure if over time, the amount of Polymer-specific glue code
will change. I suspect this file won't be needed in 1-2 Chrome versions. That's
why I was hoping to keep it under "src/js" and not encourage most people to use
it.

The reason I called it shadow_dartium.js, is to give it a more descriptive name.
You only need it in Dartium, so it's kind of the opposite of platform.js, which
is only for dart2js and polymer.js. I thought about calling it something with
"_pre" but that didn't seem very descriptive. Maybe I didn't go descriptive
enough. Would "dartium_disable_shadowdom_polyfill.js" be too long?

(Note: if we decide to replace our TemplateBinding impl with the one in
web_components, then things would get legitimately confusing. At that point
web_components starts to look like a more generally used package...)

[Siggi Cherem (dart-lang), 2014/03/06 21:26:45]

Got it, make sense.
I see - makes sense. dartium_disable_shadowdom_polyfill.js might be a bit too
long, but I'd be ok with it, especially since it's hidden in the html import, so
users are unlikely going to type it themselves.

+if (navigator.userAgent.indexOf('(Dart)') !== -1) {
+  window.Platform = window.Platform || {};
+  Platform.flags = Platform.flags || {};
+  Platform.flags.shadow = 'native';
+}