service worker: Minor refactoring in ServiceWorkerSubresourceLoader.

We don't need to make a copy of the inflight request anymore, since just
ResourceRequest is used. Also use ScopedObserver to be more robust about
removing the loader.

Add some more comments around how we handle both waitUntil() and
respondWith().

Bug: 715640
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I842a97d2af0424d3b864f64cc8f2693d94c3d63f
Reviewed-on: https://chromium-review.googlesource.com/1096579
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566331}
3 files changed