web-view: fix reloading crashed pages

When the web process crashes, we generate an error page that reloads the
view's current URI when the reload button is pressed. Unfortunately,
since WebKit r268097, the current URI is now an empty string at the time
of crash because the web process termination signal is dispatched
asynchronously after WebKit has already updated the view to contain an
empty page. This means we have to manually keep track of the previous
value of the URI. Arguably, this is a bug in WebKit, but it seems tough
to fix there and we need a workaround for now.

Note that the web process termination signal is currently only being
sent when running under flatpak. Outside flatpak, the signal is not sent
at all. That is a separate issue (WebKit#221489) that we will not fix
here.

Fixes #1447
3 jobs for mcatanzaro/#1447 in 9 minutes and 48 seconds (queued for 1 second)
Status Job ID Name Coverage
  .Pre
passed #1159612
check-code-style

00:00:56

 
  Test
passed #1159613
flatpak
flatpak

00:07:28

passed #1159614
flatpak
flatpak scanbuild

00:08:51