Introduce CryptAuthClient, a class capable of performing all CryptAuth APIs.

components/proximity_auth/cryptauth/cryptauth_api_call_flow.cc

 // Copyright 2014 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 "components/proximity_auth/cryptauth/cryptauth_api_call_flow.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "net/url_request/url_fetcher.h"
 
 namespace proximity_auth {
 
 namespace {
 
 const char kNoResponseBodyError[] = "No response body";
 const char kRequestFailedError[] = "Request failed";
 const char kHttpStatusErrorPrefix[] = "HTTP status: ";
 
 }  // namespace
 
 CryptAuthApiCallFlow::CryptAuthApiCallFlow(const GURL& request_url)
     : request_url_(request_url) {
 }
 
 CryptAuthApiCallFlow::~CryptAuthApiCallFlow() {
 }
 
 void CryptAuthApiCallFlow::Start(net::URLRequestContextGetter* context,
                                  const std::string& access_token,
                                  const std::string& serialized_request,
-                                 ResultCallback result_callback,
-                                 ErrorCallback error_callback) {
+                                 const ResultCallback& result_callback,
+                                 const ErrorCallback& error_callback) {
   serialized_request_ = serialized_request;
   result_callback_ = result_callback;
   error_callback_ = error_callback;
   OAuth2ApiCallFlow::Start(context, access_token);
 }
 
 GURL CryptAuthApiCallFlow::CreateApiCallUrl() {
   return request_url_;
 }
 
@@ skipping 22 matching lines @@
   if (source->GetStatus().status() == net::URLRequestStatus::SUCCESS) {
     error_message =
         kHttpStatusErrorPrefix + base::IntToString(source->GetResponseCode());
   } else {
     error_message = kRequestFailedError;
   }
   error_callback_.Run(error_message);
 }
 
 }  // proximity_auth