Add the reason why a save dialog was not shown to FillEventHistory.

In order to provide a better user experience, it would better know the
reason why a save dialog was not shown and improve the autofill experience.
So it is necessary to add the reason why a save dialog was not shown to
FillEventHistory.

Bug: 158328375
Test: atest FillEventHistoryTest
Test: atest InlineFillEventHistoryTest
Change-Id: I50c1e40334066d3f4844426c4b03294079a967b2