make it easier to test plugin logic

Summary:
This diff will make it easier to test a plugin in a "fully loaded" Flipper state. This makes it possible to test all the wiring of flipper, rather than the individual reducers.

This is in preparation of processing the message queue async.

Reviewed By: passy

Differential Revision: D19140879

fbshipit-source-id: 5a333abe9c7a4d0c33d1d06a105cd094cb8fc19f

src/Client.tsx

@@ -207,7 +207,7 @@ export default class Client extends EventEmitter {
     const client = this;
     // node.js doesn't support requestIdleCallback
     this.rIC =
-      typeof window === 'undefined'
+      typeof window === 'undefined' || !window.requestIdleCallback
         ? (cb: Function, _: any) => {
             cb();
           }