Pepper: Fix reentrancy problem in PepperPluginInstanceImpl.

Changes PepperPluginInstanceImpl::IsRectTopmost to not use
container_ if we are destroying the instance.

BUG=476590
Committed: https://crrev.com/2233759a94e368576ba7ce2968f77b22450d2c85
Cr-Commit-Position: refs/heads/master@{#325561}

[bbudge, 2015-04-15 23:30:52]

bbudge@chromium.org changed reviewers:
+ raymes@chromium.org

[bbudge, 2015-04-16 00:10:54]

It looks like this change is too aggressive, causing
Instance_ExecuteScriptAtInstanceShutdown to fail.

[raymes, 2015-04-16 00:21:57]

Thanks for looking at this Bill. We should be able to check whether the plugin
is in the process of being destroyed in the
PepperFlashRendererHost::OnIsRectTopmost and bail out in that case. See
PepperPluginInstanceImpl::is_deleted().

[bbudge, 2015-04-16 00:37:02]

On 2015/04/16 00:21:57, raymes wrote:
> Thanks for looking at this Bill. We should be able to check whether the plugin
> is in the process of being destroyed in the
> PepperFlashRendererHost::OnIsRectTopmost and bail out in that case. See
> PepperPluginInstanceImpl::is_deleted().

Yes, that's the safe fix. I was hoping to eliminate this kind of reentrancy but
I see that's impossible if the plugin can execute script in DidDestroy.

[raymes, 2015-04-16 23:21:44]

lgtm

[bbudge, 2015-04-16 23:22:06]

The CQ bit was checked by bbudge@chromium.org

[commit-bot: I haz the power, 2015-04-16 23:22:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1085423004/60001

[commit-bot: I haz the power, 2015-04-17 00:12:16]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-04-17 00:14:09]

Patchset 4 (id:??) landed as
https://crrev.com/2233759a94e368576ba7ce2968f77b22450d2c85
Cr-Commit-Position: refs/heads/master@{#325561}

[bbudge, 2015-05-04 21:46:53]

A revert of this CL (patchset #4 id:60001) has been created in
https://codereview.chromium.org/1122863003/ by bbudge@chromium.org.

The reason for reverting is: This didn't fix the issue (The fix will be in Blink
WebPlugin code.).