"Back" button is not returning to previously-viewed record

[philrz]

Repro is with Brim commit 803b151 and with test pcap https://archive.wrccdc.org/pcaps/2018/wrccdc.2018-03-23.010014000000000.pcap.gz (uncompress before import). It does look like this is not a new bug, though, as I was able to repro in Brim GA tagged v0.21.1 as well.

Per the attached video, repro steps:

1. Start by searching for "C1md9p1UxupPOvCs9f" and bring up the conn record in the Log Detail window
2. Click the tile for the first http event and then click the Back button. I'm brought back to the conn event as expected.
3. Click the the tile for the first files event and then click the Back button. At that point I expected to be brought back to the conn event again since it's what was just displayed. Instead the Back button brings me back to the http event, so I need to click Back yet again to get back to the original conn event.
4. If I click to other tiles, it seems to only increase the "stack" of additional events I have to click through via Back to return all the way to the original conn I'd started at.

Repro.mov

[philrz]

Verified in a nightly Brim build based on commit 226ef3b3.

Repeating the repro steps as shown in the attached video, now each time the "back" button is clicked, we go directly back to the conn record we were looking at previously.

Verify.mov

Thanks @jameskerr!