ContentPane: defer parsing/DOM instantiation until first show

[bill]

ContentPane doesn't load it's href until it's first shown (ex: that TabContainer tab is selected, or that TitlePane is opened).

Thanks to [22835], we can do the same thing when the ContentPane's initial content is specified directly via:

new dijit.layout.ContentPane({content: ...})

or

<div dojoType=dijit.layout.ContentPane>...</div>

This will be a slight performance boost.

Marking for 2.0 since it's a slight break in backwards compatibility (in case any developers are depending on those widgets being created on page load). They can still achieve that though via the preload=true flag.

[bill]

Closing this as wontfix. In ​https://github.com/ibm-js/delite (and other polyfill libraries) we shim how Custom Elements natively work, where custom elements are instantiated automatically. Therefore it's not possible to "defer parsing".