Extend UAv2 transient activation expiry time to 5sec.

We dropped the expiry time from 30sec to 1sec before launching UAv2
to give it a try, because of a lack of consensus on an acceptable value;
see the discussion on UAv2 intent thread:
https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/nkTDR8AUlwM/xsPcojA5BAAJ

With UAv2 launch, we saw some minor regressions where the use cases
would work only with a longer delay.

Note that we originally planned for a longer (even infinity) expiry time
because:
- Pre-UAv2 Chrome had 10sec in certain cases.
- Some major browsers allow infinite delay in slow event handlers.

Bug: 932577
Change-Id: If35739aacce16c14528493c6586764c2dc853251
Reviewed-on: https://chromium-review.googlesource.com/c/1479415
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#633956}(cherry picked from commit 9376d63fc9d7c717062e7e9ecbbdea6784237ed1)
Reviewed-on: https://chromium-review.googlesource.com/c/1481055
Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Cr-Commit-Position: refs/branch-heads/3626@{#879}
Cr-Branched-From: d897fb137fbaaa9355c0c93124cc048824eb1e65-refs/heads/master@{#612437}
4 files changed