test(windowCount): improve subscription assertions
test(windowCount): improve subscription assertions

Improve subscription assertions for windowCount tests.

elliotschi/rxjs,Brocco/RxJS,ReactiveX/RxJS,Igorbek/rxjs5,Igorbek/rxjs5,gluck/RxJS,kwonoj/RxJS,figueredo/RxJS,Igorbek/rxjs5,staltz/RxJSNext,gluck/RxJS,jinroh/RxJS,elliotschi/rxjs,kwonoj/RxJS,saneyuki/RxJS,martinsik/rxjs,martinsik/rxjs,RxJS-CN/RxJS-Docs-CN,Brocco/RxJS,jadbox/RxJS,elliotschi/rxjs,adrianomelo/RxJSNext,jinroh/RxJS,figueredo/RxJS,justinwoo/RxJS,benlesh/RxJS,ReactiveX/rxjs,robwormald/RxJS,adrianomelo/RxJS-1,ReactiveX/rxjs,RxJS-CN/RxJS-Docs-CN,Igorbek/rxjs5,adrianomelo/RxJS-1,robwormald/RxJS,ReactiveX/rxjs,Brocco/RxJS,IgorMinar/RxJS,jayphelps/rxjs,robwormald/RxJS,jadbox/RxJS,trxcllnt/RxJS,figueredo/RxJS,SangKa/RxJS-Docs-CN,ReactiveX/RxJS,staltz/RxJSNext,adrianomelo/RxJSNext,RxJS-CN/RxJS-Docs-CN,benlesh/RxJS,adrianomelo/RxJS-1,jadbox/RxJS,SangKa/RxJS-Docs-CN,ReactiveX/rxjs,justinwoo/RxJS,benlesh/RxJS,trxcllnt/RxJS,martinsik/rxjs,gluck/RxJS,trxcllnt/RxJS,jayphelps/rxjs,jinroh/RxJS,kwonoj/RxJS,justinwoo/RxJS,jayphelps/rxjs,IgorMinar/RxJS,kwonoj/RxJS,justinwoo/RxJS,saneyuki/RxJS,trxcllnt/RxJS,RxJS-CN/RxJS-Docs-CN,ReactiveX/RxJS,staltz/RxJSNext,figueredo/RxJS,Brocco/RxJS,gluck/RxJS,SangKa/RxJS-Docs-CN,staltz/RxJSNext,adrianomelo/RxJSNext,elliotschi/rxjs,martinsik/rxjs,robwormald/RxJS,benlesh/RxJS,adrianomelo/RxJSNext,ReactiveX/RxJS,jayphelps/rxjs,jayphelps/rxjs,SangKa/RxJS-Docs-CN,adrianomelo/RxJS-1,jadbox/RxJS,jinroh/RxJS