Support restart of FirestoreClient #12802

Job	Run time
Build Firestore	9m 12s
Test Firestore (test:browser)	4m 18s
Test Firestore (test:travis)	4m 0s
Test Firestore Compatible on Firefox	6m 21s
Test Nightly Firestore with Chrome	0s
Test Firestore (test:lite:browser)	1m 30s
Test Firestore on Firefox (test:browser)	4m 9s
Test Firestore (test:browser:prod:nameddb)	4m 17s
Test Firestore on Firefox (test:travis)	3m 54s
Test Firestore (test:lite:browser:nameddb)	1m 23s
Test Firestore Compatible	4m 12s
Test Firestore on Firefox (test:lite:browser)	1m 45s
Test Firestore on Firefox (test:browser:prod:nameddb)	4m 9s
Test Firestore on Firefox (test:lite:browser:nameddb)	2m 1s
Check all required tests results	1s
	51m 12s

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