Fix UAF in new Mojo EDK.
The problem was that MessagePipeDispatcher was calling Broker::CloseMessagePipe asynchronously, and in between the time that the posted task was run the MPD could be deleted and called back by the channel for another error.
Since all these methods are now called on the IO thread only, fix this by allowing reentrancy for CloseMessagePipe.
BUG=561803
TEST= linux_chromeos browser_tests pass with new EDK
Review URL: https://codereview.chromium.org/1537593002
Cr-Commit-Position: refs/heads/master@{#365782}
CrOS-Libchrome-Original-Commit: 7f48f0a4073d7ec74eea40aa85a9ebfa506236ce
5 files changed