Refactor CryptAuth component to be more testable.

components/proximity_auth/cryptauth/cryptauth_api_call_flow.h

 // 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.
 
 #ifndef COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_API_CALL_FLOW_H
 #define COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_API_CALL_FLOW_H
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "google_apis/gaia/oauth2_api_call_flow.h"
 
 namespace proximity_auth {
 
 // Google API call flow implementation underlying all CryptAuth API calls.
 // CryptAuth is a Google service that manages authorization and cryptographic
 // credentials for users' devices (eg. public keys).
 class CryptAuthApiCallFlow : public OAuth2ApiCallFlow {
  public:
   typedef base::Callback<void(const std::string& serialized_response)>
       ResultCallback;
   typedef base::Callback<void(const std::string& error_message)> ErrorCallback;
 
-  CryptAuthApiCallFlow(const GURL& request_url);
+  CryptAuthApiCallFlow();
   ~CryptAuthApiCallFlow() override;
 
   // Starts the API call.
+  //   request_url: The URL endpoint of the API request.
   //   context: The URL context used to make the request.
   //   access_token: The access token for whom to make the to make the request.
   //   serialized_request: A serialized proto containing the request data.
   //   result_callback: Called when the flow completes successfully with a
   //       serialized response proto.
   //   error_callback: Called when the flow completes with an error.
-  virtual void Start(net::URLRequestContextGetter* context,
+  virtual void Start(const GURL& request_url,
+                     net::URLRequestContextGetter* context,
                      const std::string& access_token,
                      const std::string& serialized_request,
                      const ResultCallback& result_callback,
                      const ErrorCallback& error_callback);
 
  protected:
   // Reduce the visibility of OAuth2ApiCallFlow::Start() to avoid exposing
   // overloaded methods.
   using OAuth2ApiCallFlow::Start;
 
   // google_apis::OAuth2ApiCallFlow:
   GURL CreateApiCallUrl() override;
   std::string CreateApiCallBody() override;
   std::string CreateApiCallBodyContentType() override;
   void ProcessApiCallSuccess(const net::URLFetcher* source) override;
   void ProcessApiCallFailure(const net::URLFetcher* source) override;
 
  private:
   // The URL of the CryptAuth endpoint serving the request.
-  const GURL request_url_;
+  GURL request_url_;
 
   // Serialized request message proto that will be sent in the API request.
   std::string serialized_request_;
 
   // Callback invoked with the serialized response message proto when the flow
   // completes successfully.
   ResultCallback result_callback_;
 
   // Callback invoked with an error message when the flow fails.
   ErrorCallback error_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(CryptAuthApiCallFlow);
 };
 
 }  // namespace proximity_auth
 
 #endif  // COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_API_CALL_FLOW_H