* Change LOG(INFO) to LOG(WARNING) to reduce noise in log.

* Better handling of delegate==NULL case, not just use shortcut to return safe value, but rather exercise the following path assuming the call to delegate returns some safe default.

BUG=chromium-os:8958
TEST=Open incognito window, close all tabs in normal window, then close all tabs in incognito window and do not observe any crash

Review URL: http://codereview.chromium.org/5114001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@66391 0039d316-1c4b-4281-b951-d872f2087c98