Overwrite undefined candidate index #12996

Job	Run time
Build Firestore	8m 22s
Test Firestore Compatible on Firefox	5m 47s
Test Firestore (test:browser)	9m 8s
Test Firestore (test:travis)	4m 3s
Test Firestore Compatible	4m 12s
Test Firestore on Firefox (test:browser)	9m 59s
Test Firestore (test:lite:browser)	1m 20s
Test Nightly Firestore with Chrome	0s
Test Firestore (test:browser:prod:nameddb)	8m 32s
Test Firestore on Firefox (test:travis)	3m 51s
Test Firestore (test:lite:browser:nameddb)	1m 43s
Test Firestore on Firefox (test:lite:browser)	2m 1s
Test Firestore Compatible on Webkit	4m 21s
Test Firestore on Firefox (test:browser:prod:nameddb)	10m 23s
Test Firestore on Webkit (test:browser)	10m 31s
Test Firestore on Firefox (test:lite:browser:nameddb)	2m 28s
Test Firestore on Webkit (test:lite:browser)	1m 32s
Test Firestore on Webkit (test:browser:prod:nameddb)	9m 48s
Test Firestore on Webkit (test:lite:browser:nameddb)	1m 44s
Check all required tests results	1s
	1h 39m 46s

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