[Blimp] Adds Blimp EngineSession and ClientSession skeleton

blimp/common/proto/server_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 server-originating browser control messages.
-//
-// Current definitions are just placeholders and are NOT final.
-// Feel free to modify this interface as necessary during feature work.
-
-syntax = "proto2";
-
-option optimize_for = LITE_RUNTIME;
-
-message StatusArgs {
-  optional string url = 1;
-  optional int32 loading_progress = 2;
-  // Add error code, error message, status strings, etc.
-}
-
-message ResetSessionArgs {
-}
-
-message ErrorArgs {
-  enum ErrorCode {
-    UNKNOWN = 1;
-    UNRESPONSIVE = 2;
-    SERVER_ERROR = 3;
-  }
-
-  optional ErrorCode error_code = 1;
-  optional int32 server_error_code = 2;
-}
-
-message ServerControlMessage {
-  enum Type {
-    ERROR = 1;
-    STATUS = 2;
-  }
-  optional Type type = 1;
-
-  optional ErrorArgs error = 1000;
-  optional StatusArgs status = 1001;
-}