Cleanup ExtensionDownloadsEventRouter on download manager shutdown

Cleanup ExtensionDownloadsEventRouter on download manager shutdown.

BUG=Debug browser_tests occasionally crash with failed DCHECK in ExtensionDownloadsEventRouter.


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=148807

[asanka, 2012-07-27 16:10:22]

EDER expects to be destroyed on the UI thread. But EDER is owned by
ChromeDownloadManagerDelegate. When running tests, we can occasionally end the
test and tear down message loops while tasks that hold references to CDMD are
still pending. This is usually because filename determination is still in
progress. In such cases, CDMD could be destroyed on other threads (including the
main thread).

This fix is to destroy EDER when the download manager is going down at
DownloadManagerDelegate::Shutdown(). That way the EDER can be cleaned up
properly on the UI thread when it is no longer needed.

[benjhayden, 2012-07-27 16:30:09]

LGTM Nice catch!

[commit-bot: I haz the power, 2012-07-27 18:22:12]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/asanka@chromium.org/10829058/1

[commit-bot: I haz the power, 2012-07-27 21:11:21]

Change committed as 148807