Use an explicit PID for duplicating Pepper handles rather than the Channel's.

ppapi/proxy/host_dispatcher.h

Index: ppapi/proxy/host_dispatcher.h
diff --git a/ppapi/proxy/host_dispatcher.h b/ppapi/proxy/host_dispatcher.h
index 98a7ad5e5ed4280c8972ef7132ed3990cb6bc5c5..1b0c9a7ccf97b4fe694551ec00e7dcbab9834f66 100644
--- a/ppapi/proxy/host_dispatcher.h
+++ b/ppapi/proxy/host_dispatcher.h
@@ -58,6 +58,7 @@ class PPAPI_PROXY_EXPORT HostDispatcher : public Dispatcher {
   // The delegate pointer must outlive this class, ownership is not
   // transferred.
   virtual bool InitHostWithChannel(Delegate* delegate,
+                                   base::ProcessId peer_pid,
                                    const IPC::ChannelHandle& channel_handle,
                                    bool is_client,
                                    const Preferences& preferences);