Summary:
This change attaches our event handlers as soon as the ws is created.
As a consequence, we need to wait until the server has created any necessary instances required to process incoming requests.
To achieve this, I created a type called `Lazy`.
This type wraps around a value and a promise to that value. Callers can check if the value is set. If not, callers can wait for it.
Ultimately, the value can be set outside of the promise itself.
Reviewed By: passy
Differential Revision: D37284939
fbshipit-source-id: 17dec548d7155a3d65440c9584cec07cbb826c37
8c67b049ab