Code: MediaStreamImpl::~MediaStreamImpl() {
  DCHECK(!peer_connection_handler_);
  if (dependency_factory_.get())
    dependency_factory_->ReleasePeerConnectionFactory();
  if (network_manager_) {
    if (chrome_worker_thread_.IsRunning()) {
       chrome_worker_thread_.message_loop()->PostTask(FROM_HERE, base::Bind(
           &MediaStreamImpl::DeleteIpcNetworkManager,
           base::Unretained(this)));
     } else {
       NOTREACHED() << "Worker thread not running.";
     }
  }
}

Vulnerability Type: DoS 
CWE ID: CWE-399
Summary: Use-after-free vulnerability in Google Chrome before 20.0.1132.43 allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors related to tables that have sections.
Commit Message: Explicitly stopping thread in MediaStreamImpl dtor to avoid any racing issues.

This may solve the below bugs.

BUG=112408,111202
TEST=content_unittests

Review URL: https://chromiumcodereview.appspot.com/9307058

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@120222 0039d316-1c4b-4281-b951-d872f2087c98