Make IPC channels track their peer process ID

ipc/ipc_channel_win.cc

Index: ipc/ipc_channel_win.cc
===================================================================
--- ipc/ipc_channel_win.cc	(revision 130443)
+++ ipc/ipc_channel_win.cc	(working copy)
@@ -37,6 +37,7 @@
       ALLOW_THIS_IN_INITIALIZER_LIST(input_state_(this)),
       ALLOW_THIS_IN_INITIALIZER_LIST(output_state_(this)),
       pipe_(INVALID_HANDLE_VALUE),
+      peer_pid_(base::kNullProcessId),
       waiting_connect_(mode & MODE_SERVER_FLAG),
       processing_incoming_(false),
       ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)),
@@ -159,6 +160,7 @@
     listener()->OnChannelError();
     return;
   }
+  peer_pid_ = claimed_pid;
   // validation completed.
   validate_client_ = false;
   listener()->OnChannelConnected(claimed_pid);
@@ -467,6 +469,10 @@
   channel_impl_->set_listener(listener);
 }
 
+base::ProcessId Channel::peer_pid() const {
+  return channel_impl_->peer_pid();
+}
+
 bool Channel::Send(Message* message) {
   return channel_impl_->Send(message);
 }