I've seen it being flaky on iPad and iPhone X causing the entire suit to fail. I've disabled it in 

[0723/104629.124979:WARNING:gaia_auth_fetcher.cc(963)] Incomprehensible response from Google Accounts servers.
../../ios/chrome/browser/metrics/ukm_egtest.mm:118: error: -[UKMTestCase testHistoryDelete] : Exception: AssertionFailedException
Exception Name: AssertionFailedException
Exception Reason: ((base::test::ios::WaitUntilConditionOrTimeout( kSyncUKMOperationsTimeout, condition)) is true) failed
Exception Details: Failed to assert whether UKM was enabled or not.
Bundle ID: org.chromium.gtest.generic-unit-test
Stack Trace: (
	0   EarlGrey                            0x0000000118ae4799 -[GREYDefaultFailureHandler handleException:details:] + 1305
	1   ios_chrome_integration_egtests      0x000000010abbb87d _ZN12_GLOBAL__N_116AssertUKMEnabledEb + 1837
	2   ios_chrome_integration_egtests      0x000000010abc6956 -[UKMTestCase testHistoryDelete] + 6102
	3   CoreFoundation                      0x0000000116e97c6c __invoking___ + 140
	4   CoreFoundation                      0x0000000116e97b40 -[NSInvocation invoke] + 320