sync: Introduce ModelTypeRegistry and helpers

sync/internal_api/sync_manager_impl.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 SYNC_INTERNAL_API_SYNC_MANAGER_H_
 #define SYNC_INTERNAL_API_SYNC_MANAGER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 16 matching lines @@
 #include "sync/notifier/invalidator_state.h"
 #include "sync/syncable/directory_change_delegate.h"
 #include "sync/util/cryptographer.h"
 #include "sync/util/time.h"
 
 namespace syncer {
 
 class SyncAPIServerConnectionManager;
 class WriteNode;
 class WriteTransaction;
+class ModelTypeRegistry;
 
 namespace sessions {
 class SyncSessionContext;
 }
 
 // SyncManager encapsulates syncable::Directory and serves as the parent of all
 // other objects in the sync API.  If multiple threads interact with the same
 // local sync repository (i.e. the same sqlite database), they should share a
 // single SyncManager instance.  The caller should typically create one
 // SyncManager for the lifetime of a user session.
@@ skipping 260 matching lines @@
   // This can be called from any thread, but only between calls to
   // OpenDirectory() and ShutdownOnSyncThread().
   WeakHandle<SyncManager::ChangeObserver> change_observer_;
 
   ObserverList<SyncManager::Observer> observers_;
 
   // The ServerConnectionManager used to abstract communication between the
   // client (the Syncer) and the sync server.
   scoped_ptr<SyncAPIServerConnectionManager> connection_manager_;
 
+  // Maintains state that affects the way we interact with different sync types.
+  // This state will be updated during configuration cycles, but otherwise

[tim (not reviewing), 2014/01/08 19:33:42]

Perhaps saying "updated when routing info changes, such as when entering or
exiting a configuration cycle" (or "changes when entering or exiting a
configuration cycle" if you want to avoid "routing info").

[rlarocque, 2014/01/09 00:31:18]

Done.  I went with the second suggestion.

+  // remains constant.
+  scoped_ptr<ModelTypeRegistry> model_type_registry_;
+
   // A container of various bits of information used by the SyncScheduler to
   // create SyncSessions.  Must outlive the SyncScheduler.
   scoped_ptr<sessions::SyncSessionContext> session_context_;
 
   // The scheduler that runs the Syncer. Needs to be explicitly
   // Start()ed.
   scoped_ptr<SyncScheduler> scheduler_;
 
   // A multi-purpose status watch object that aggregates stats from various
   // sync components.
@@ skipping 43 matching lines @@
   scoped_ptr<SyncEncryptionHandlerImpl> sync_encryption_handler_;
 
   base::WeakPtrFactory<SyncManagerImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncManagerImpl);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_SYNC_MANAGER_H_