[FSSDK-10643] make event processor injectable (#948) #796

Job	Run time
crossbrowser_and_umd_unit_tests	6h 0m 14s
lint	3m 25s
unit_tests (16)	3m 20s
unit_tests (18)	1m 32s
unit_tests (20)	1m 31s
unit_tests (22)	1m 29s
fullstack_production_suite / test	3s
integration_tests / test	10s
lint_markdown_files / lint	3m 1s
Coveralls coverage	4s
	6h 14m 49s

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