Prepare to abstract PersistedData by making it part of the configurator.

components/update_client/configurator.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_UPDATE_CLIENT_CONFIGURATOR_H_
 #define COMPONENTS_UPDATE_CLIENT_CONFIGURATOR_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/memory/ref_counted.h"
 
 class GURL;
 class PrefService;
 
 namespace base {
 class SequencedTaskRunner;
 class Version;
 }
 
 namespace net {
 class URLRequestContextGetter;
 }
 
 namespace update_client {
 
 class OutOfProcessPatcher;
+class PersistedData;
 
 // Controls the component updater behavior.
 // TODO(sorin): this class will be split soon in two. One class controls
 // the behavior of the update client, and the other class controls the
 // behavior of the component updater.
 class Configurator : public base::RefCountedThreadSafe<Configurator> {
  public:
   // Delay in seconds from calling Start() to the first update check.
   virtual int InitialDelay() const = 0;
 
@@ skipping 80 matching lines @@
   // Gets a task runner to a blocking pool of threads suitable for worker jobs.
   virtual scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner()
       const = 0;
 
   // Returns a PrefService that the update_client can use to store persistent
   // update information. The PrefService must outlive the entire update_client,
   // and be safe to access from the thread the update_client is constructed
   // on.
   // Returning null is safe and will disable any functionality that requires
   // persistent storage.
   virtual PrefService* GetPrefService() const = 0;

[Devlin, 2017/05/16 23:03:09]

A quick codesearch indicates that this is only used in
components/update_client/update_engine.cc where we created the persisted data. 
Since that's abstracted out, can we remove this?  Or is this actually used
elsewhere that's not showing up?

[Minh X. Nguyen, 2017/06/01 21:04:19]

Done.

 
   // Returns true if the Chrome is installed for the current user only, or false
   // if Chrome is installed for all users on the machine. This function must be
   // called only from a blocking pool thread, as it may access the file system.
   virtual bool IsPerUserInstall() const = 0;
 
+  // Returns a PersistedData object that update_client can use to store
+  // persistent update information.
+  virtual std::unique_ptr<PersistedData> CreateMetadata() const = 0;
+
  protected:
   friend class base::RefCountedThreadSafe<Configurator>;
 
   virtual ~Configurator() {}
 };
 
 }  // namespace update_client
 
 #endif  // COMPONENTS_UPDATE_CLIENT_CONFIGURATOR_H_