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

chrome/common/render_messages.h

Index: chrome/common/render_messages.h
diff --git a/chrome/common/render_messages.h b/chrome/common/render_messages.h
index ca43e8d08d9f316b0abb1470ea7b28468a65cd68..90dc3dbac5ff4364d6f28c43b3919333af32a662 100644
--- a/chrome/common/render_messages.h
+++ b/chrome/common/render_messages.h
@@ -541,7 +541,7 @@ IPC_MESSAGE_ROUTED3(ChromeViewHostMsg_ForwardMessageToExternalHost,
 // a new instance of the Native Client process. The browser will launch
 // the process and return an IPC channel handle. This handle will only
 // be valid if the NaCl IPC proxy is enabled.
-IPC_SYNC_MESSAGE_CONTROL4_3(ChromeViewHostMsg_LaunchNaCl,
+IPC_SYNC_MESSAGE_CONTROL4_4(ChromeViewHostMsg_LaunchNaCl,
                             GURL /* manifest_url */,
                             int /* render_view_id */,
                             uint32 /* permission_bits */,
@@ -549,6 +549,7 @@ IPC_SYNC_MESSAGE_CONTROL4_3(ChromeViewHostMsg_LaunchNaCl,
                             std::vector<nacl::FileDescriptor>
                                 /* imc channel handles */,
                             IPC::ChannelHandle /* ipc_channel_handle */,
+                            base::ProcessId /* plugin_pid */,
                             int /* plugin_child_id */)
 
 // A renderer sends this to the browser process when it wants to