Summary: In previous `XHRInterceptor`, it sometimes crashes when restarting the network inspector because the id of the XHR objects are not unique all time. Fix this in diff by adding a global id "generator" for all intercepted xhr objects in order to make it safe across inspector restarts.
Reviewed By: davidaurelio
Differential Revision: D3641624
fbshipit-source-id: f9a1589f278023243aa182d3da93ce69c985587c