NavigationControllerBrowserTest* in content_browsertests is flaky.

Findit has detected 3 flake occurrences of tests below within
the past 24 hours:

NavigationControllerBrowserTest.LoadCommittedDetails_IsSameDocument
NavigationControllerBrowserTest.PruningOfEntriesForDynamicFrames_ParentNavigatedAway

Please try to find and revert the culprit if the culprit is obvious.
Otherwise please find an appropriate owner.