Avoid UAF in PepperUDP/TCPSocketMessageFilter

Avoid UAF in PepperUDP/TCPSocketMessageFilter

We were trying to access BrowserPpapiHost or ResourceHost after they may have
been destroyed. Instead cache IsPotentiallySecurePluginContext in an instance
variable to report in UMA.

BUG=515943
Committed: https://crrev.com/2ee190edb17da8bedaae4d640887e243d26087d3
Cr-Commit-Position: refs/heads/master@{#342261}

[raymes, 2015-08-06 01:17:05]

The CQ bit was checked by raymes@chromium.org to run a CQ dry run

[raymes, 2015-08-06 01:17:12]

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

[commit-bot: I haz the power, 2015-08-06 01:17:23]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1276763002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1276763002/1

[commit-bot: I haz the power, 2015-08-06 01:35:24]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-06 01:35:24]

Dry run: Try jobs failed on following builders:
  linux_chromium_gn_dbg on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  linux_chromium_gn_rel on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[raymes, 2015-08-06 01:46:14]

The CQ bit was checked by raymes@chromium.org

[raymes, 2015-08-06 01:46:24]

The CQ bit was unchecked by raymes@chromium.org

[raymes, 2015-08-06 01:46:32]

The CQ bit was checked by raymes@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-06 01:46:50]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1276763002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1276763002/20001

[commit-bot: I haz the power, 2015-08-06 03:29:08]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-06 03:29:09]

Dry run: Try jobs failed on following builders:
  win_chromium_x64_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[bbudge, 2015-08-06 18:24:26]

lgtm

[raymes, 2015-08-07 00:10:57]

The CQ bit was checked by raymes@chromium.org

[commit-bot: I haz the power, 2015-08-07 00:12:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1276763002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1276763002/20001

[commit-bot: I haz the power, 2015-08-07 01:46:43]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-08-07 01:47:22]

Patchset 2 (id:??) landed as
https://crrev.com/2ee190edb17da8bedaae4d640887e243d26087d3
Cr-Commit-Position: refs/heads/master@{#342261}