Abandon prerenders upon render thread shutdown.

Abandon prerenders upon render thread shutdown.

Have PrerenderDispatcher abandon its current prerenders when
the renderer is about to shut down -- doing so later isn't
supported as Blink is about to disappear.

Along with this, on the Blink side, weaken the reference that
a Prerender object keep to its PrerenderClient. The latter
should keep the former alive, but not vice versa -- if no one
is referring to the client within Blink, it can be GCed.
This avoids prolonged retention of prerendering Blink objects.

R=
BUG=604325
Committed: https://crrev.com/dee5cd76d7b11963fc8f404db008f169bef62b74
Cr-Commit-Position: refs/heads/master@{#387912}

[sof, 2016-04-18 11:33:53]

sigbjornf@opera.com changed reviewers:
+ gavinp@chromium.org, haraken@chromium.org, tkent@chromium.org

[sof, 2016-04-18 11:33:53]

please take a look.

This prevents shutdown crashes upon e.g. the user closing the browser. If the
prerendering dispatcher is allowed to release its outstanding prerender objects
upon it shutting down, Blink will no longer be around and failure awaits.

https://codereview.chromium.org/1900583002/diff/1/third_party/WebKit/Source/p...
File third_party/WebKit/Source/platform/Prerender.h (right):

https://codereview.chromium.org/1900583002/diff/1/third_party/WebKit/Source/p...
third_party/WebKit/Source/platform/Prerender.h:90: WeakMember<PrerenderClient>
m_client;
An alternative to this is to have the WebPrivatePtr<Prerender> be weak instead.

[haraken, 2016-04-18 12:50:41]

Another option would be to make RenderThreadImpl::shutdown call detachRenderer
before it calls blink::shutdown?

[sof, 2016-04-18 13:05:25]

On 2016/04/18 12:50:41, haraken wrote:
> Another option would be to make RenderThreadImpl::shutdown call detachRenderer
> before it calls blink::shutdown?

Ah yes, there's no need to make this Blink driven - the prerender dispatcher is
a RenderThreadObserver.

[sof, 2016-04-18 13:21:59]

On 2016/04/18 13:05:25, sof wrote:
> On 2016/04/18 12:50:41, haraken wrote:
> > Another option would be to make RenderThreadImpl::shutdown call
detachRenderer
> > before it calls blink::shutdown?
> 
> Ah yes, there's no need to make this Blink driven - the prerender dispatcher
is
> a RenderThreadObserver.

Done.

[sof, 2016-04-18 13:27:14]

Description was changed from

==========
Notify embedder prerendering support that Blink is shutting down.

To prevent the prerendering support from accessing Blink after it
has shut down, issue a notification just before shutting down.

The embedder must let go of and abandon all prerendering requests
from the renderer at that point; doing so any later is unsafe
and guaranteed to crashedly fail.

R=
BUG=604325
==========

to

==========
Abandon prerenders upon render thread shutdown.

Have PrerenderDispatcher abandon its current prerenders when
the renderer is about to shut down -- doing so later isn't
supported as Blink is about to disappear.

Along with this, on the Blink side, weaken the reference that
a Prerender object keep to its PrerenderClient. The latter
should keep the former alive, but not vice versa -- if no one
is referring to the client within Blink, it can be GCed.
This avoids prolonged retention of prerendering Blink objects.

R=
BUG=604325
==========

[haraken, 2016-04-18 14:23:39]

LGTM

[sof, 2016-04-18 14:44:55]

sigbjornf@opera.com changed reviewers:
+ cbentzel@chromium.org

[sof, 2016-04-18 14:44:56]

+cbentzel@ to reviewer list - ptal? (not sure if gavinp@ is actively reviewing
atm.)

[gavinp, 2016-04-18 15:16:09]

On 2016/04/18 14:44:56, sof wrote:
> +cbentzel@ to reviewer list - ptal? (not sure if gavinp@ is actively reviewing
> atm.)

I'm reviewing, don't worry. Taking a look now.

[gavinp, 2016-04-18 15:17:42]

lgtm.

[sof, 2016-04-18 15:29:28]

On 2016/04/18 15:17:42, gavinp wrote:
> lgtm.

many thanks

[sof, 2016-04-18 15:29:40]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-04-18 15:29:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1900583002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1900583002/20001

[commit-bot: I haz the power, 2016-04-18 15:33:49]

Description was changed from

==========
Abandon prerenders upon render thread shutdown.

Have PrerenderDispatcher abandon its current prerenders when
the renderer is about to shut down -- doing so later isn't
supported as Blink is about to disappear.

Along with this, on the Blink side, weaken the reference that
a Prerender object keep to its PrerenderClient. The latter
should keep the former alive, but not vice versa -- if no one
is referring to the client within Blink, it can be GCed.
This avoids prolonged retention of prerendering Blink objects.

R=
BUG=604325
==========

to

==========
Abandon prerenders upon render thread shutdown.

Have PrerenderDispatcher abandon its current prerenders when
the renderer is about to shut down -- doing so later isn't
supported as Blink is about to disappear.

Along with this, on the Blink side, weaken the reference that
a Prerender object keep to its PrerenderClient. The latter
should keep the former alive, but not vice versa -- if no one
is referring to the client within Blink, it can be GCed.
This avoids prolonged retention of prerendering Blink objects.

R=
BUG=604325
==========

[commit-bot: I haz the power, 2016-04-18 15:33:51]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-04-18 15:35:18]

Description was changed from

==========
Abandon prerenders upon render thread shutdown.

Have PrerenderDispatcher abandon its current prerenders when
the renderer is about to shut down -- doing so later isn't
supported as Blink is about to disappear.

Along with this, on the Blink side, weaken the reference that
a Prerender object keep to its PrerenderClient. The latter
should keep the former alive, but not vice versa -- if no one
is referring to the client within Blink, it can be GCed.
This avoids prolonged retention of prerendering Blink objects.

R=
BUG=604325
==========

to

==========
Abandon prerenders upon render thread shutdown.

Have PrerenderDispatcher abandon its current prerenders when
the renderer is about to shut down -- doing so later isn't
supported as Blink is about to disappear.

Along with this, on the Blink side, weaken the reference that
a Prerender object keep to its PrerenderClient. The latter
should keep the former alive, but not vice versa -- if no one
is referring to the client within Blink, it can be GCed.
This avoids prolonged retention of prerendering Blink objects.

R=
BUG=604325

Committed: https://crrev.com/dee5cd76d7b11963fc8f404db008f169bef62b74
Cr-Commit-Position: refs/heads/master@{#387912}
==========

[commit-bot: I haz the power, 2016-04-18 15:35:19]

Patchset 2 (id:??) landed as
https://crrev.com/dee5cd76d7b11963fc8f404db008f169bef62b74
Cr-Commit-Position: refs/heads/master@{#387912}