BrowserPlugin: Cleanup ChildFrameCompositingHelper and fix lifetime issue

BrowserPlugin: Cleanup ChildFrameCompositingHelper and fix lifetime issue

ChildFrameCompositingHelper had a raw pointer to WebPluginContainer, and
BrowserPluginManager, which is not safe. In another patch,
see https://codereview.chromium.org/140073002/, there is an access to the
container after it is deleted, which is causing a use-after-free
crash on the win_rel bot.

BUG=334531
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=248628

[kenrb, 2014-01-31 23:44:37]

One comment, but otherwise lgtm.

https://codereview.chromium.org/133233012/diff/80001/content/renderer/child_f...
File content/renderer/child_frame_compositing_helper.cc (right):

https://codereview.chromium.org/133233012/diff/80001/content/renderer/child_f...
content/renderer/child_frame_compositing_helper.cc:77: if (!browser_plugin_)
nit: is this check necessary? If BrowerPlugin owns the compositing helper then
it shouldn't be possible to become NULL.

[Fady Samuel, 2014-02-03 18:04:20]

https://codereview.chromium.org/133233012/diff/80001/content/renderer/child_f...
File content/renderer/child_frame_compositing_helper.cc (right):

https://codereview.chromium.org/133233012/diff/80001/content/renderer/child_f...
content/renderer/child_frame_compositing_helper.cc:77: if (!browser_plugin_)
On 2014/01/31 23:44:37, kenrb wrote:
> nit: is this check necessary? If BrowerPlugin owns the compositing helper then
> it shouldn't be possible to become NULL.

I just attempted this. There are a couple of callbacks that keep the
CompositingHelper alive:

https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/c...

https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/c...

[Fady Samuel, 2014-02-03 19:17:21]

+creis@ for OWNER review.

[Charlie Reis, 2014-02-03 20:57:15]

LGTM

[Fady Samuel, 2014-02-03 21:10:13]

The CQ bit was checked by fsamuel@chromium.org

[commit-bot: I haz the power, 2014-02-03 21:11:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/fsamuel@chromium.org/133233012/80001

[commit-bot: I haz the power, 2014-02-04 00:25:30]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-02-04 00:25:30]

Change committed as 248628

[commit-bot: I haz the power, 2014-02-04 00:25:31]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-02-04 00:25:32]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-02-04 00:25:34]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-02-04 00:25:38]

CQ bit was unchecked on CL. Ignoring.