Fix crash in ServiceWorkerRegistrationHandle

Fix crash in ServiceWorkerRegistrationHandle

Before this patch, when register() fails to install a worker, it would
result in ServiceWorkerRegistrationHandle::OnRegisterFailed nulling out
its reference to the registration in order to allow the registration
to die. This was flawed for two reasons:
- When the handle is destructed, it would dereference the null pointer.
- SWRegistrationHandle is responsible for listening for ref count changes from
Blink-side about the corresponding JavaScript ServiceWorkerRegistration object.
It's a weird state for Handle to forget about the Chromium-side registration
while Blink-side is alive. The Chromium-side Registration lifetime should be
tied to Blink's.

BUG=384119, 396400
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=289597

[falken, 2014-08-14 08:07:03]

WDYT? The alternative is to clear registration_ on Failed() like we already do,
and just get that registration_ is not NULL in the dtor. That seems error-prone
though, it's more obvious that while the Handle for the Reg is alive, the Reg is
alive too; and the Handle only dies the Blink is done with its registration.

[nhiroki, 2014-08-14 08:38:47]

Thank you for working on this. LGTM.

On 2014/08/14 08:07:03, falken wrote:
> WDYT? The alternative is to clear registration_ on Failed() like we already
do,
> and just get that registration_ is not NULL in the dtor. That seems
error-prone
> though, it's more obvious that while the Handle for the Reg is alive, the Reg
is
> alive too; and the Handle only dies the Blink is done with its registration.

+1 for matching their lifetime. It looks really simpler than the alternative.

[nhiroki, 2014-08-14 08:39:08]

https://codereview.chromium.org/461233004/diff/20001/content/browser/service_...
File content/browser/service_worker/service_worker_registration_handle.cc
(right):

https://codereview.chromium.org/461233004/diff/20001/content/browser/service_...
content/browser/service_worker/service_worker_registration_handle.cc:35:
ServiceWorkerRegistrationHandle::~ServiceWorkerRegistrationHandle() {
Can we have DCHECK for |registration_| here?

[falken, 2014-08-14 09:07:21]

Thanks!

https://codereview.chromium.org/461233004/diff/20001/content/browser/service_...
File content/browser/service_worker/service_worker_registration_handle.cc
(right):

https://codereview.chromium.org/461233004/diff/20001/content/browser/service_...
content/browser/service_worker/service_worker_registration_handle.cc:35:
ServiceWorkerRegistrationHandle::~ServiceWorkerRegistrationHandle() {
On 2014/08/14 08:39:07, nhiroki wrote:
> Can we have DCHECK for |registration_| here?

Done.

[falken, 2014-08-14 09:08:00]

The CQ bit was checked by falken@chromium.org

[commit-bot: I haz the power, 2014-08-14 09:10:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/falken@chromium.org/461233004/40001

[commit-bot: I haz the power, 2014-08-14 15:31:32]

Committed patchset #3 (40001) as 289597