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This CL allows users to navigate to the activity log page via URL even
if the extension ID specified in the URL is invalid/uninstalled. This
allows the user to see install-time activities in real-time via the
following steps:

1) Navigate to the activity log via URL
2) Click on the real-time tab
3) Install the extension with the ID in the activity log's URL. Note
   that a listener for extension activities is already present for the
   extension ID.
4) In the real-time tab, the extension's install-time activities should
   appear.

Screenshots: https://imgur.com/a/Niyc3S8

Bug: 832354
Change-Id: Ifaa0c3ea57d295f8657f067c610a093170e909a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1620346
Commit-Queue: Kelvin Jiang <kelvinjiang@chromium.org>
Reviewed-by: Esmael El-Moslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664073}