Do not create the content directive when using ShadowDom

[naomiblack]

This creates a performance issue for apps that rely on ShadowDom. Reported by @jbdeboer.

[vsavkin]

@jbdeboer we do not have a global setting for enabling/disabling shadow DOM. The decision is made by every component.

It is possible to add a global setting, but it will require either changing generators or using some static variable.

Content.registerContentTag = false;
final app = applicationFactory().addModule(module);
app.run();

There are a lot of complications that arise from that.

Considering all of this, do we have to implement it? Or can we use the following workaround?

final app = applicationFactory().addModule(module);
app.ngModule.bindings.remove(new Key(Content));
app.run();

What are your thoughts?