Remove all blimp engine code

blimp/engine/common/blimp_user_agent.cc

-// 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.
-
-#include "blimp/engine/common/blimp_user_agent.h"
-
-#include <string>
-
-#include "components/version_info/version_info.h"
-#include "content/public/common/user_agent.h"
-
-namespace blimp {
-namespace engine {
-
-namespace {
-
-std::string client_os_info = "Linux; Android 5.1.1";
-
-}  // namespace
-
-std::string GetBlimpEngineUserAgent() {
-  return content::BuildUserAgentFromOSAndProduct(
-      client_os_info,
-      version_info::GetProductNameAndVersionForUserAgent() + " Mobile");
-}
-
-void SetClientOSInfo(std::string os_version_info) {
-  client_os_info = os_version_info;
-}
-
-}  // namespace engine
-}  // namespace blimp