Fix for crash when attaching a frame in WebUI renderer.

Fix for crash when attaching a frame in WebUI renderer.

It crashes when trying to install property on "chrome" object in Javascript.
Before the patch, the code assumes the "chrome" either does not exist
or is an object. Apparently, it holds "undefined" value in WebUI pages.

BUG=

Committed: https://crrev.com/e1b79c756bf3ee66a4211f06d59af0c95a17d49e
Cr-Commit-Position: refs/heads/master@{#297621}

[Krzysztof Olczyk, 2014-09-26 13:51:00]

kolczyk@opera.com changed reviewers:
+ avi@chromium.org, jamesr@chromium.org, jochen@chromium.org, sky@chromium.org

[Krzysztof Olczyk, 2014-09-26 13:51:01]

Hi guys,

could you please take a look at this fix for a CHECK() abort accompanied by the
browser test
which demonstrates this reproduce before the fix.

[Avi (use Gerrit), 2014-09-26 15:09:28]

Please give a bug number in the description.

I don't know about webui so I can't comment on the fix. Come back to me when the
experts there have spoken.

[Mike West, 2014-09-30 07:51:46]

mkwst@chromium.org changed reviewers:
+ mkwst@chromium.org

[Mike West, 2014-09-30 07:51:47]

Drive-by non-OWNER comments. This looks pretty reasonable: one request below.

https://codereview.chromium.org/611483002/diff/1/content/renderer/web_ui_exte...
File content/renderer/web_ui_extension.cc (right):

https://codereview.chromium.org/611483002/diff/1/content/renderer/web_ui_exte...
content/renderer/web_ui_extension.cc:76: if (chrome_value.IsEmpty() ||
!chrome_value->IsObject()) {
Please adjust skia_benchmarking_extension and memory_benchmarking_extension as
well; right now this code hits the bug because it's the first one to be
initialized. If the ordering of 'RenderViewImpl::didClearWindowObject' changes,
one of those might run into the same issue.

It might even be worthwhile to extract this snippet to a static method somewhere
to ensure that 'chrome' always gets set up correctly.

[jochen (gone - plz use gerrit), 2014-09-30 08:46:52]

lgtm

[Krzysztof Olczyk, 2014-10-01 09:10:47]

The CQ bit was checked by kolczyk@opera.com

[commit-bot: I haz the power, 2014-10-01 09:12:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/611483002/20001

[commit-bot: I haz the power, 2014-10-01 10:07:06]

Committed patchset #2 (id:20001) as 1f8f04f28ed6a1c96f114f5c709184879a0d410c

[commit-bot: I haz the power, 2014-10-01 10:08:06]

Patchset 2 (id:??) landed as
https://crrev.com/e1b79c756bf3ee66a4211f06d59af0c95a17d49e
Cr-Commit-Position: refs/heads/master@{#297621}