Revert "UsageStats: New event query API with specific event types."

Revert submission 25109517-usageevents_filter_query

Reason for revert: build breakage

Reverted changes: /q/submissionid:25109517-usageevents_filter_query

Change-Id: Ibadb44bd0b388d4ea5dc012227d43a3254be3899
10 files changed