reproduce it once and it appears to be occuring when the ListenSocket attempts to pass an
OnObjectSignaled notification to a delegate which is the web server which has already been destroyed

Attempted fix is to destroy the ListenSocket in the destructor of the web server.

BUG=none
TEST=Existing chrome frame tests.

TBR=amit

Review URL: http://codereview.chromium.org/6155009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71125 0039d316-1c4b-4281-b951-d872f2087c98