Remove all blimp engine code

blimp/engine/common/blimp_user_agent.h

Index: blimp/engine/common/blimp_user_agent.h
diff --git a/blimp/engine/common/blimp_user_agent.h b/blimp/engine/common/blimp_user_agent.h
deleted file mode 100644
index e64af88712fcee7499ad3871ad7b4891f3dba9eb..0000000000000000000000000000000000000000
--- a/blimp/engine/common/blimp_user_agent.h
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright 2016 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.
-
-#ifndef BLIMP_ENGINE_COMMON_BLIMP_USER_AGENT_H_
-#define BLIMP_ENGINE_COMMON_BLIMP_USER_AGENT_H_
-
-#include <string>
-
-#include "content/public/common/content_client.h"
-
-namespace blimp {
-namespace engine {
-
-std::string GetBlimpEngineUserAgent();
-void SetClientOSInfo(std::string client_os_info);
-
-}  // namespace engine
-}  // namespace blimp
-
-#endif  // BLIMP_ENGINE_COMMON_BLIMP_USER_AGENT_H_