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

chrome/common/extensions/extension_messages.h

Index: chrome/common/extensions/extension_messages.h
diff --git a/chrome/common/extensions/extension_messages.h b/chrome/common/extensions/extension_messages.h
index 03ade298d32f690bcaf3133cd4bc3661363594a4..4b634a67a207d488f148ea9d1fccbbce4afa7d7d 100644
--- a/chrome/common/extensions/extension_messages.h
+++ b/chrome/common/extensions/extension_messages.h
@@ -297,10 +297,15 @@ 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