The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6db7057d79c85f333b24036b475ab49ff80ba68b

commit 6db7057d79c85f333b24036b475ab49ff80ba68b
Author: Devlin Cronin <rdevlin.cronin@chromium.org>
Date: Fri Dec 21 23:23:24 2018

[Extensions Cleanup] Remove linked_ptr from EventRouter code

Remove linked_ptr usage from extensions event-related code, including
event_router.* and lazy_event_dispatcher.*. Most of these were easy
changes, where the object didn't actually have to be linked. One
exception is in the lazy event dispatching. Previously, we would store
the linked_ptr in a callback while waiting for the extension background
page to start up. Now, we instead have to create a copy of the event.
This is slightly less efficient, since it is an additional copy
(potentially even an additional copy per browser context per extension),
but realistically, this won't happen frequently (because the background
context would be around for at least 5 seconds after any event).

Bug:  913604 
Change-Id: I9cb534f69f1839a7fbfe640490317221c5448884
Reviewed-on: https://chromium-review.googlesource.com/c/1370721
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618665}
[modify] https://crrev.com/6db7057d79c85f333b24036b475ab49ff80ba68b/chrome/browser/extensions/api/web_request/web_request_api_unittest.cc
[modify] https://crrev.com/6db7057d79c85f333b24036b475ab49ff80ba68b/extensions/browser/event_router.cc
[modify] https://crrev.com/6db7057d79c85f333b24036b475ab49ff80ba68b/extensions/browser/event_router.h
[modify] https://crrev.com/6db7057d79c85f333b24036b475ab49ff80ba68b/extensions/browser/events/lazy_event_dispatcher.cc
[modify] https://crrev.com/6db7057d79c85f333b24036b475ab49ff80ba68b/extensions/browser/events/lazy_event_dispatcher.h