correctly load scripts in chrome & firefox #5331

Job	Run time
Build extensions	5m 47s
Test	2m 9s
ember-try (ember-lts-3.16)	1m 5s
ember-try (ember-lts-3.20)	1m 18s
ember-try (ember-lts-3.24)	1m 18s
ember-try (ember-lts-3.28)	1m 14s
ember-try (ember-release)	1m 38s
ember-try (ember-beta)	1m 49s
ember-try (ember-canary)	1m 14s
ember-try (ember-default-no-prototype-extensions)	1m 13s
Publish bookmarklet	0s
Publish GitHub release	0s
Publish Firefox extension	0s
Publish Chrome extension	0s
Publish npm package	0s
	18m 45s

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