[Extensions] Handle content scripts and web requests in activity log

This CL fixes some display issues and unhandled cases for the activity
log: for content scripts and web requests in particular.

Show one entry in the activity log per invocation of the content script.

Split the web request activity into one for every web request action
taken. This un-masks some information in the activity log object for
the  web request.

Screenshots: https://imgur.com/a/NmNXRO4

Bug: 832354
Change-Id: I69bcbb319ccd2957ff6ebe9cc9d272d7d1bdc3f0
Reviewed-on: https://chromium-review.googlesource.com/c/1399427
Commit-Queue: Kelvin Jiang <kelvinjiang@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623095}
8 files changed