Likely unhandled syscall in Chromium cricket::UDPPort::OnReadPacket causes false positive uninits

_From [rnk@google.com](https://code.google.com/u/rnk@google.com/) on January 12, 2012 12:15:22_

I don't have the logs and I haven't attempted to reproduce locally, but I'm assuming this is a system call out write that we're not handling appropriately.

Example report: http://build.chromium.org/p/chromium.fyi/builders/Windows%20Tests%20%28DrMemory%20full%29/builds/332/steps/memory%20test%3A%20remoting/logs/stdio ~~Dr.M~~ Error `#2`: UNINITIALIZED READ: reading register eflags
~~Dr.M~~ # 0 cricket::StunMessage::Read [third_party\libjingle\source\talk\p2p\base\stun.cc:152]
~~Dr.M~~ # 1 cricket::Port::GetStunMessage [third_party\libjingle\source\talk\p2p\base\port.cc:245]
~~Dr.M~~ # 2 cricket::Port::OnReadPacket [third_party\libjingle\source\talk\p2p\base\port.cc:209]
~~Dr.M~~ # 3 cricket::UDPPort::OnReadPacket [third_party\libjingle\source\talk\p2p\base\udpport.cc:109]
~~Dr.M~~ # 4 sigslot::_connection4::emit [third_party\libjingle\source\talk\base\sigslot.h:1960]
~~Dr.M~~ # 5 sigslot::signal4::operator() [third_party\libjingle\source\talk\base\sigslot.h:2511]
~~Dr.M~~ # 6 talk_base::AsyncUDPSocket::OnReadEvent [third_party\libjingle\source\talk\base\asyncudpsocket.cc:127]
~~Dr.M~~ # 7 sigslot::_connection1::emit [third_party\libjingle\source\talk\base\sigslot.h:1819]
~~Dr.M~~ # 8 sigslot::signal1::operator() [third_party\libjingle\source\talk\base\sigslot.h:2313]
~~Dr.M~~ # 9 talk_base::SocketDispatcher::OnEvent [third_party\libjingle\source\talk\base\physicalsocketserver.cc:1077]
~~Dr.M~~ `#10` talk_base::PhysicalSocketServer::Wait [third_party\libjingle\source\talk\base\physicalsocketserver.cc:1596]
~~Dr.M~~ `#11` talk_base::MessageQueue::Get [third_party\libjingle\source\talk\base\messagequeue.cc:242]
~~Dr.M~~ `#12` talk_base::Thread::ProcessMessages [third_party\libjingle\source\talk\base\thread.cc:499]
~~Dr.M~~ `#13` talk_base::Thread::Run [third_party\libjingle\source\talk\base\thread.cc:361]
~~Dr.M~~ `#14` remoting::`anonymous namespace'::JingleMessagePump::Run [remoting\jingle_glue\jingle_thread.cc:31]
\~~Dr.M~~`#15`MessageLoop::RunInternal [base\message_loop.cc:417]
\~~Dr.M~~`#16`MessageLoop::RunHandler [base\message_loop.cc:390]
\~~Dr.M~~`#17` MessageLoop::Run [base\message_loop.cc:300]
~~Dr.M~~ Note: @0:04:31.323 in thread 3380
~~Dr.M~~ Note: instruction: jz $0x01226282

We should add a label for FalsePos-Syscall or Component-Syscall or something so we can easily find unhandled system call bugs.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=744_