Check Extension in extension_error_ui_util

Check Extension in extension_error_ui_util.
BUG=361082
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=263068

[Finnur, 2014-04-10 12:24:02]

https://codereview.chromium.org/226743005/diff/1/chrome/browser/ui/webui/exte...
File chrome/browser/ui/webui/extensions/extension_error_ui_util.cc (right):

https://codereview.chromium.org/226743005/diff/1/chrome/browser/ui/webui/exte...
chrome/browser/ui/webui/extensions/extension_error_ui_util.cc:87: return;
Looks like it would fix the crash, but do we have a good understanding as to why
we end up in this situation?

[Devlin, 2014-04-10 16:21:08]

https://codereview.chromium.org/226743005/diff/1/chrome/browser/ui/webui/exte...
File chrome/browser/ui/webui/extensions/extension_error_ui_util.cc (right):

https://codereview.chromium.org/226743005/diff/1/chrome/browser/ui/webui/exte...
chrome/browser/ui/webui/extensions/extension_error_ui_util.cc:87: return;
On 2014/04/10 12:24:02, Finnur wrote:
> Looks like it would fix the crash, but do we have a good understanding as to
why
> we end up in this situation?  

My suspicion is that, since we really only enter this code path when an
extension encounters an error, the extension may have crashed, and entered the
terminated state (which is the only state which
ExtensionService::GetExtensionById() doesn't check).  I think that subbing in
ExtensionRegistry::GetExtensionById(EVERYTHING) will solve this, but, on the
off-chance it doesn't, we should fail gracefully (at least in release builds). 
Added a NOTREACHED() so we can tell in Debug builds if this truly fixed the
problem.

[Finnur, 2014-04-10 16:37:49]

LGTM

[Devlin, 2014-04-10 17:53:26]

The CQ bit was checked by rdevlin.cronin@chromium.org

[commit-bot: I haz the power, 2014-04-10 17:53:29]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rdevlin.cronin@chromium.org/226743005/...

[commit-bot: I haz the power, 2014-04-10 20:31:08]

Change committed as 263068