Run pending tasks in ~TestBrowserThreadBundle.

This makes sure we run all remaining tasks in tests. This should be the
case even for ExecutionMode::QUEUED as documented here:
https://cs.chromium.org/chromium/src/base/test/scoped_task_environment.h?l=42

Also lift the restriction to only flush tasks in !MOCK_TIME && !QUEUED modes
which is unnecessary now that TestBrowserThreadBundle is-a
ScopedTaskEnvironment (http://crrev.com/616622).

Bug: 708584
Change-Id: I52773e27d3875bd246bb1cd7eea92c9e11fc70bf
Reviewed-on: https://chromium-review.googlesource.com/c/1480460
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637288}
1 file changed