Eliminate race condition when setting model early on TimelineView

Eliminate race condition when setting model early on TimelineView

When calling TimelineView.model setter before its dom is ready, we
would break because model setup assumes readiness. This patch just
defers the set call until the ready call.

As part of this CL, I eliminate useless copies of children elements
stored on the instance, and split out the ready function into created
and ready components based on their need of DOM or not.

TBR=nduca
BUG=catapult:#2252

[nduca, 2016-08-20 02:09:28]

The CQ bit was checked by nduca@chromium.org

[commit-bot: I haz the power, 2016-08-20 02:09:34]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-20 02:57:20]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-20 02:57:20]

Try jobs failed on following builders:
  Catapult Mac Tryserver on master.tryserver.client.catapult (JOB_FAILED,
https://build.chromium.org/p/tryserver.client.catapult/builders/Catapult%20Ma...)