Hack to restrict runtime API to dev channel rather than experimental.

chrome/common/extensions/extension_messages.h

 // Copyright (c) 2012 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.
 
 // IPC messages for extensions.
 // Multiply-included message file, hence no include guard.
 
 #include "base/shared_memory.h"
 #include "base/values.h"
 #include "chrome/common/extensions/extension.h"
@@ skipping 279 matching lines @@
                     std::string /* channel_name */,
                     std::string /* tab_json */,
                     std::string /* source_extension_id */,
                     std::string /* target_extension_id */)
 
 // Deliver a message sent with ExtensionHostMsg_PostMessage.
 IPC_MESSAGE_ROUTED2(ExtensionMsg_DeliverMessage,
                     int /* target_port_id */,
                     std::string /* message */)
 
+// Dispatch the Port.onDisconnect event for message channels.
 IPC_MESSAGE_ROUTED2(ExtensionMsg_DispatchOnDisconnect,
                     int /* port_id */,
                     bool /* connection_error */)
 
+// Informs the renderer what channel (dev, beta, stable, etc) is running.
+IPC_MESSAGE_CONTROL1(ExtensionMsg_SetChannel,
+                     int /* channel */)
+
 // Messages sent from the renderer to the browser.
 
 // A renderer sends this message when an extension process starts an API
 // request. The browser will always respond with a ExtensionMsg_Response.
 IPC_MESSAGE_ROUTED1(ExtensionHostMsg_Request,
                     ExtensionHostMsg_Request_Params)
 
 // A renderer sends this message when an extension process starts an API
 // request. The browser will always respond with a ExtensionMsg_Response.
 IPC_MESSAGE_CONTROL2(ExtensionHostMsg_RequestForIOThread,
@@ skipping 117 matching lines @@
 IPC_MESSAGE_ROUTED0(ExtensionHostMsg_IncrementLazyKeepaliveCount)
 
 // Informs the browser there is one less thing keeping the lazy background page
 // alive.
 IPC_MESSAGE_ROUTED0(ExtensionHostMsg_DecrementLazyKeepaliveCount)
 
 // Fetches a globally unique ID (for the lifetime of the browser) from the
 // browser process.
 IPC_SYNC_MESSAGE_CONTROL0_1(ExtensionHostMsg_GenerateUniqueID,
                             int /* unique_id */)