[CRD iOS] Implementing save to keychain and user defaults for login info. Refactor remoting service.

remoting/client/ios/facade/host_list_fetcher.cc

 // Copyright 2017 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 "remoting/client/ios/facade/host_list_fetcher.h"
 
 #include <thread>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 11 matching lines @@
     const scoped_refptr<net::URLRequestContextGetter>&
         url_request_context_getter)
     : url_request_context_getter_(url_request_context_getter) {}
 
 HostListFetcher::~HostListFetcher() {}
 
 // TODO(nicholss): This was written assuming only one request at a time. Fix
 // that. For the moment it will work to make progress in the app.
 void HostListFetcher::RetrieveHostlist(const std::string& access_token,
                                        const HostlistCallback& callback) {
+  // TODO(nicholss): There is a bug here if two host list fetches are happening
+  // at the same time there will be a dcheck thrown. Fix this for release.
   DCHECK(!access_token.empty());
   DCHECK(callback);
   DCHECK(!hostlist_callback_);
 
   hostlist_callback_ = callback;
 
   request_ = net::URLFetcher::Create(GURL(kHostListProdRequestUrl),
                                      net::URLFetcher::GET, this);
   request_->SetRequestContext(url_request_context_getter_.get());
   request_->AddExtraRequestHeader("Authorization: OAuth " + access_token);
@@ skipping 58 matching lines @@
   DCHECK(source);
 
   std::vector<HostInfo> hostlist;
   if (!ProcessResponse(&hostlist)) {
     hostlist.clear();
   }
   base::ResetAndReturn(&hostlist_callback_).Run(hostlist);
 }
 
 }  // namespace remoting