Stub out initial NavigationController browser implementation

This is the initial cut for the browser-side NavigationControllerDispatcherHost,
and all the various related support plumbing to hook up two initial messages.

BUG= 285976

Review URL: https://chromiumcodereview.appspot.com/23615009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224585 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ipc/ipc_message_start.h b/ipc/ipc_message_start.h
index dc9be23..a8cca535 100644
--- a/ipc/ipc_message_start.h
+++ b/ipc/ipc_message_start.h
@@ -89,7 +89,8 @@
   LocalDiscoveryMsgStart,
   PowerMonitorMsgStart,
   EncryptedMediaMsgStart,
-  LastIPCMsgStart      // Must come last.
+  ServiceWorkerMsgStart,
+  LastIPCMsgStart  // Must come last.
 };
 
 #endif  // IPC_IPC_MESSAGE_START_H_