[Blimp Net] Add EngineAuthHandler.

blimp/common/proto/protocol_control.proto

 // Copyright 2015 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 definitions for browser control messages.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
-import "size.proto";
-
 package blimp;
 
-message ControlMessage {
+// Contains Client->Engine information to establish a authenticated connection.
+message StartConnectionMessage {
+  optional string client_token = 1;
+  optional int32 protocol_version = 2;
+}
+
+message ProtocolControlMessage {
   enum Type {
     UNKNOWN = 0;
 
-    // Client <=> Server types.
-    CREATE_TAB = 1;
-    CLOSE_TAB = 2;
-
     // Client => Server types.
-    SIZE = 3;
+    START_CONNECTION = 1;
   }
 
   optional Type type = 1;
 
-  // Feature-specific messages follow.
-  // Only one of these fields may be set per ControlMessage.
-  optional SizeMessage resize = 1000;
+  optional StartConnectionMessage start_connection = 1000;
 }