Clean up NavigationContext usage in HistoryTabHelper::DidFinishNavigation

Notable changes:
 - Remove IsDownload check, because it's a subset of existing
   HasCommitted check;
 - Update comment related to HasCommitted to mention aborted navigations;
 - Remove IsSameDocument check, because HasCommitted now returns true
   for successful same-document navigations;

Bug: 921097
Change-Id: I145a24a80f5d853b2ab2da415d822ef64dc94dd3
Reviewed-on: https://chromium-review.googlesource.com/c/1416392
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623463}
1 file changed