Don't keep the lazy background page alive after a view with a Pepper plugin is closed

Don't keep the lazy background page alive after a view with a Pepper plugin is closed.

A ref counting mechanism was added in
https://codereview.chromium.org/1117023002/ to keep event/background
pages from being unloaded if they had a plugin on them. However, plugins
in app windows created from the background page are still counted in
this ref counting. And if a plugin is embedded in an app window for a
chrome app, and the window is closed without removing the plugin first,
the browser message was never delivered to update the ref count.

The fix is to trigger the ref counter change only for for the NaCl
instances attached to the background pages.

BUG=521053
Committed: https://crrev.com/e3baba1f5a1c747382c5623364503ac451fb6ddb
Cr-Commit-Position: refs/heads/master@{#354899}

[emaxx, 2015-10-19 19:38:00]

emaxx@chromium.org changed reviewers:
+ bbudge@chromium.org, rockot@chromium.org

[emaxx, 2015-10-19 19:38:01]

rockot@chromium.org: Please review changes in chrome/browser/*,
extensions/browser/*

bbudge@chromium.org: Please review changes in ppapi/*, chrome/chrome_tests.gypi

[Ken Rockot(use gerrit already), 2015-10-19 22:02:53]

extensions lgtm

[bbudge, 2015-10-19 22:09:54]

I don't understand how the test works. Where do you test that the background
page is unloaded?

[emaxx, 2015-10-19 22:13:40]

On 2015/10/19 22:09:54, bbudge wrote:
> I don't understand how the test works. Where do you test that the background
> page is unloaded?

The lazy background page is unloaded when the tab (with the NaCl plugin) is
closed. So this is tested in lazy_background_page_apitest.cc in line 371: the
page_complete.WaitUntilClosed() condition will never finish if the background
page stays alive.

[bbudge, 2015-10-19 22:33:15]

Thanks LGTM

[emaxx, 2015-10-19 22:38:43]

The CQ bit was checked by emaxx@chromium.org

[commit-bot: I haz the power, 2015-10-19 22:39:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1414783002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1414783002/1

[commit-bot: I haz the power, 2015-10-19 22:45:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-19 22:46:31]

Patchset 1 (id:??) landed as
https://crrev.com/e3baba1f5a1c747382c5623364503ac451fb6ddb
Cr-Commit-Position: refs/heads/master@{#354899}