Allow on-* event handlers on <sky-element>.

Allow on-* event handlers on <sky-element>.

Now instead of calling addEventListener inside the created() callback you just
add on-{eventName} attributes to the <sky-element> around your element
definition. The attribute defines what method on your element to call when the
event with {eventName} is dispatched through your element.

Implementing this required refactoring how sky-element.sky stored information
from each registered element. Now instead of storing just a map of templates
we store a map of ElementRegistration objects which have metadata about the
element. Future patches will combine this system with the element registration
system in sky-binder.

R=ojan@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/6c501416f074c22d6bd424bea3a76ffc601dff6e

[ojan, 2015-01-13 01:02:46]

lgtm

https://codereview.chromium.org/845283003/diff/20001/sky/framework/sky-elemen...
File sky/framework/sky-element/sky-element.sky (right):

https://codereview.chromium.org/845283003/diff/20001/sky/framework/sky-elemen...
sky/framework/sky-element/sky-element.sky:75: getEventHandler(eventName) {
Nit: I'd put an extra line break after each method. This code is super cramped.

[esprehn, 2015-01-13 02:25:26]

Committed patchset #3 (id:40001) manually as
6c501416f074c22d6bd424bea3a76ffc601dff6e (presubmit successful).