Summary:
This does 2 things:
- modernize the component to use ES6 + flow
- assign `rootTag` to the child context
Each view in RN has its own `reactTag`. The reactTag for a root view is called `rootTag`. When there are multiple react root views active within the app (e.g. in a hybrid environment), rootTag is the only reliable "label" to differentiate them. This is especially useful when we want to limit an event/activity on a particular root view, instead of affecting all active root views. This allows components to do:
```
class Foo extends React.Component {
static contextTypes = {
rootTag: React.PropTypes.number,
};
componentDidMount() {
// Get the root tag of this component, which is static for all components under the same root view
console.log(this.context.rootTag);
}
}
```
In a pure JS RN app environment, there will always be exactly 1 root view, so `rootTag` may usually be ignored.
Reviewed By: yungsters
Differential Revision: D4130376
fbshipit-source-id: 559b67615f487bad754b5832ad4a02bcef05be2a
fb7fe2d4e8