Stub out initial NavigationController browser implementation

content/common/nav_controller_messages.h

Index: content/common/nav_controller_messages.h
diff --git a/content/common/nav_controller_messages.h b/content/common/nav_controller_messages.h
new file mode 100644
index 0000000000000000000000000000000000000000..a9c29f1bb8b4611dd66fa269cc1b8d8ae59eb7ff
--- /dev/null
+++ b/content/common/nav_controller_messages.h
@@ -0,0 +1,27 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Message definition file, included multiple times, hence no include guard.
+
+#include "base/strings/string16.h"
+#include "ipc/ipc_message_macros.h"
+#include "ipc/ipc_param_traits.h"
+#include "url/gurl.h"
+
+#define IPC_MESSAGE_START NavControllerMsgStart
+
+IPC_MESSAGE_CONTROL3(NavControllerHostMsg_RegisterController,

[Tom Sepez, 2013/09/13 21:48:34]

nit: Generally, I'd split these into browser -> renderer and renderer -> browser
sections, with a comment indicating which way the messages are going for each
section (even though the HostMsg_ indicates this).

+                     int32 /* registry_id */,
+                     string16 /* scope */,

[Tom Sepez, 2013/09/13 21:48:34]

What is scope?  Can you give an example?  In particluar, if its some structured
list we'd prefer that it not be tunnelled through IPC using strings.  If not,
then ... nevermind.

+                     GURL /* script_url */)
+
+IPC_MESSAGE_CONTROL1(NavControllerMsg_ControllerReady, int32 /* registry_id */)

[Tom Sepez, 2013/09/13 21:48:34]

nit: maybe a comment about "Response to ..." in all places.

+
+IPC_MESSAGE_CONTROL2(NavControllerHostMsg_UnregisterController,
+                     int32 /* registry_id */,
+                     string16 /* scope */)
+
+IPC_MESSAGE_CONTROL2(NavControllerMsg_ControllerUnregistered,
+                     int32 /* registry_id */,
+                     string16 /* scope */)