[Sync] Remove SyncClient dep from SyncBackendRegistrar.

components/sync/driver/glue/sync_backend_registrar.h

 // Copyright 2012 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_SYNC_DRIVER_GLUE_SYNC_BACKEND_REGISTRAR_H_
 #define COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_REGISTRAR_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/engine/model_safe_worker.h"
 #include "components/sync/engine/sync_manager.h"
 
 namespace syncer {
 
 class ChangeProcessor;
-class SyncClient;
 struct UserShare;
 
 // A class that keep track of the workers, change processors, and
 // routing info for the enabled sync types, and also routes change
 // events to the right processors.
 class SyncBackendRegistrar : public SyncManager::ChangeDelegate {
  public:
+  using ModelSafeWorkerFactory =
+      base::Callback<scoped_refptr<ModelSafeWorker>(ModelSafeGroup)>;
+
   // |name| is used for debugging. Must be created on the UI thread.
-  SyncBackendRegistrar(const std::string& name, SyncClient* sync_client);
+  SyncBackendRegistrar(const std::string& name,
+                       ModelSafeWorkerFactory worker_factory);
 
   // A SyncBackendRegistrar is owned by a SyncBackendHostImpl. It is destroyed
   // by SyncBackendHostImpl::Shutdown() which performs the following operations
   // on the UI thread:
   //
   //   1) Call SyncBackendRegistrar::RequestWorkerStopOnUIThread().
   //   2) Post a SyncBackendHostCore::DoShutdown() task to the sync thread. This
   //      task destroys SyncManager which holds a SyncBackendRegistrar pointer.
   //   3) Take ownership of the sync thread.
   //   4) Post a task to delete the SyncBackendRegistrar on the sync thread.
@@ skipping 62 matching lines @@
                         const ImmutableChangeRecordList& changes) override;
   void OnChangesComplete(ModelType model_type) override;
 
   void GetWorkers(std::vector<scoped_refptr<ModelSafeWorker>>* out);
   void GetModelSafeRoutingInfo(ModelSafeRoutingInfo* out);
 
  private:
   typedef std::map<ModelSafeGroup, scoped_refptr<ModelSafeWorker>> WorkerMap;
   typedef std::map<ModelType, ChangeProcessor*> ProcessorMap;
 
-  // Add a worker for |group| to the worker map if one can be created.
-  void MaybeAddWorker(ModelSafeGroup group);
+  // Add a worker for |group| to the worker map if one is successfully created
+  // by |worker_factory|.
+  void MaybeAddWorker(ModelSafeWorkerFactory worker_factory,
+                      ModelSafeGroup group);
 
   // Returns the change processor for the given model, or null if none
   // exists.  Must be called from |group|'s native thread.
   ChangeProcessor* GetProcessor(ModelType type) const;
 
   // Must be called with |lock_| held.  Simply returns the change
   // processor for the given type, if it exists.  May be called from
   // any thread.
   ChangeProcessor* GetProcessorUnsafe(ModelType type) const;
 
   // Return true if |model_type| lives on the current thread.  Must be
   // called with |lock_| held.  May be called on any thread.
   bool IsCurrentThreadSafeForModel(ModelType model_type) const;
 
   // Returns model safe group that should be assigned to type when it is first
   // configured (before activation). Returns GROUP_PASSIVE for directory types
   // and GROUP_NON_BLOCKING for non-blocking types.
   ModelSafeGroup GetInitialGroupForType(ModelType type) const;
 
   // Name used for debugging.
   const std::string name_;
 
-  // A pointer to the sync client.
-  SyncClient* const sync_client_;
-
   // Checker for the UI thread (where this object is constructed).
   base::ThreadChecker ui_thread_checker_;
 
   // Protects all variables below.
   mutable base::Lock lock_;
 
   // Workers created by this SyncBackendRegistrar.
   WorkerMap workers_;
 
   ModelSafeRoutingInfo routing_info_;
 
   // The change processors that handle the different data types.
   ProcessorMap processors_;
 
   // The types that were enabled as of the last configuration. Updated on each
   // call to ConfigureDataTypes as well as SetInitialTypes.
   ModelTypeSet last_configured_types_;
 
   // Set of types with non-blocking implementation (as opposed to directory
   // based).
   ModelTypeSet non_blocking_types_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendRegistrar);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_REGISTRAR_H_