ipc: Create an unforgeable mechanism to get the process id of the sender.

ipc/ipc_channel_win.cc

Index: ipc/ipc_channel_win.cc
diff --git a/ipc/ipc_channel_win.cc b/ipc/ipc_channel_win.cc
index a01a272feba8d7c7b8cb157aab83208d1159a263..f59f046772e44fa410b2eda5bd1cca1411558789 100644
--- a/ipc/ipc_channel_win.cc
+++ b/ipc/ipc_channel_win.cc
@@ -243,6 +243,10 @@ void ChannelWin::HandleInternalMessage(const Message& msg) {
   listener()->OnChannelConnected(claimed_pid);
 }
 
+base::ProcessId ChannelWin::GetSenderPID() {
+  return GetPeerPID();
+}
+
 bool ChannelWin::DidEmptyInputBuffers() {
   // We don't need to do anything here.
   return true;