Move Mojo channel initialization closer to IPC::Channel setup

content/common/web_ui_setup.mojom

Index: content/common/web_ui_setup.mojom
diff --git a/content/common/web_ui_setup.mojom b/content/common/web_ui_setup.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..d61d96ceddfe44f2865b8fb3c563cab99666daf7
--- /dev/null
+++ b/content/common/web_ui_setup.mojom
@@ -0,0 +1,16 @@
+// Copyright 2014 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.
+
+module content {
+
+[Peer=WebUISetup]
+interface WebUISetupClient {
+};
+
+[Peer=WebUISetupClient]
+interface WebUISetup {
+  SetWebUIHandle(int32 view_routing_id, handle<message_pipe> web_ui_handle);
+};
+
+}