Merged revision(s) 1534846 from tomcat/trunk:
- Prevent recursive invocation of Runnables by Room.invokeAndWait() to prevent errors like ConcurrentModificationException when Room.broadcastRoomMessage() iterates over an ArrayList and then calls Room.invokeAndWait() recursivly, iterating again over the array.
- Add comment about blocking Session.close() method.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1534848 13f79535-47bb-0310-9956-ffa450edef68