Improve SkyElement.

Improve SkyElement.

- Don't stamp the template repeatedly when attaching.
- Don't use __proto__
- Store the template in an external map instead of a property on the prototype.
- Add a created() callback.
- Allow creating a SkyElement with no associated <template> or ShadowRoot.

R=rafaelw@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/8a89ee55bafcb5615ec287714ed1b22005b71e6d

[esprehn, 2014-11-12 07:06:03]

esprehn@chromium.org changed reviewers:
+ rafaelw@chromium.org

[rafaelw, 2014-11-12 12:00:53]

lgtm

https://codereview.chromium.org/715203002/diff/20001/sky/framework/sky-elemen...
File sky/framework/sky-element/sky-element.sky (right):

https://codereview.chromium.org/715203002/diff/20001/sky/framework/sky-elemen...
sky/framework/sky-element/sky-element.sky:66: templates.set(prototype.name,
template);
Nit: You want weak semantics here, so I'd use a Symbol (I assume you are trying
to avoid creating the .template_ expando).

[esprehn, 2014-11-12 18:10:25]

On 2014/11/12 at 12:00:53, rafaelw wrote:
> lgtm
> 
>
https://codereview.chromium.org/715203002/diff/20001/sky/framework/sky-elemen...
> File sky/framework/sky-element/sky-element.sky (right):
> 
>
https://codereview.chromium.org/715203002/diff/20001/sky/framework/sky-elemen...
> sky/framework/sky-element/sky-element.sky:66: templates.set(prototype.name,
template);
> Nit: You want weak semantics here, so I'd use a Symbol (I assume you are
trying to avoid creating the .template_ expando).

Not sure what you mean by weak semantics, the object will live forever because
of the registerElement(). Not sure how you're suggesting using a Symbol.

[rafaelw, 2014-11-12 18:43:45]

Yeah, I was thinking of the lifetime of the template being tied to the proto,
but it makes sense that registerElement keeps it alive forever anyway, so nm.

still lgtm

[esprehn, 2014-11-12 20:32:43]

Committed patchset #2 (id:20001) manually as
8a89ee55bafcb5615ec287714ed1b22005b71e6d (presubmit successful).