[DevTools] Application>Clear Site Data: stop service worker when unregistering it
[DevTools] Application>Clear Site Data: stop service worker when unregistering it

We should stop the service worker before unregistering it.

Originally, clicking "Clear site data" will unregister the service worker. In
Application>Service Workers, the service worker's tab title is marked as
"deleted", but its "status" says it's still running.

Bug: 894783
Change-Id: Ib1550cfab8274a27495bb795501f54e9a19f6a36
Reviewed-on: https://chromium-review.googlesource.com/c/1480725
Reviewed-by: Dmitry Gozman <0ca14b32cbb359a30ac562af27dd84cc2813eacb@chromium.org>
Commit-Queue: Haihong Li (Harley) <9cb4eae756ad117d277e87e55452ee4270dafbc5@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#635263}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3dc09a0d59439a0867ebd50ab6784691e12450ea
ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend