[Sync] Add plumbing of context from client to server

sync/engine/directory_update_handler.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 SYNC_ENGINE_DIRECTORY_UPDATE_HANDLER_H_
 #define SYNC_ENGINE_DIRECTORY_UPDATE_HANDLER_H_
 
 #include <map>
 
 #include "base/basictypes.h"
@@ skipping 29 matching lines @@
 // Each instance of this class represents a particular type in the
 // syncable::Directory.  It can store and retreive that type's progress markers.
 // It can also process a set of received SyncEntities and store their data.
 class SYNC_EXPORT_PRIVATE DirectoryUpdateHandler : public UpdateHandler {
  public:
   DirectoryUpdateHandler(syncable::Directory* dir,
                          ModelType type,
                          scoped_refptr<ModelSafeWorker> worker);
   virtual ~DirectoryUpdateHandler();
 
-  // Fills the given parameter with the stored progress marker for this type.
+  // UpdateHandler implementation.
   virtual void GetDownloadProgress(
       sync_pb::DataTypeProgressMarker* progress_marker) const OVERRIDE;
-
-  // Processes the contents of a GetUpdates response message.
-  //
-  // Should be invoked with the progress marker and set of SyncEntities from a
-  // single GetUpdates response message.  The progress marker's type must match
-  // this update handler's type, and the set of SyncEntities must include all
-  // entities of this type found in the response message.
+  virtual void GetDataTypeContext(
+      sync_pb::DataTypeContext* context) const OVERRIDE;
   virtual void ProcessGetUpdatesResponse(
       const sync_pb::DataTypeProgressMarker& progress_marker,
       const SyncEntityList& applicable_updates,
       sessions::StatusController* status) OVERRIDE;
-
-  // If there are updates to apply, apply them on the proper thread.
-  // Delegates to ApplyUpdatesImpl().
+  virtual void ProcessDataTypeContextMutation(
+      const sync_pb::DataTypeContext& mutated_context) OVERRIDE;
   virtual void ApplyUpdates(sessions::StatusController* status) OVERRIDE;
-
-  // Apply updates on the sync thread.  This is for use during initial sync
-  // prior to model association.
   virtual void PassiveApplyUpdates(sessions::StatusController* status) OVERRIDE;
 
  private:
   friend class DirectoryUpdateHandlerApplyUpdateTest;
   friend class DirectoryUpdateHandlerProcessUpdateTest;
 
   // Sometimes there is nothing to do, so we can return without doing anything.
   bool IsApplyUpdatesRequired();
 
   // Processes the given SyncEntities and stores their data in the directory.
@@ skipping 24 matching lines @@
   scoped_refptr<ModelSafeWorker> worker_;
 
   scoped_ptr<sync_pb::GarbageCollectionDirective> cached_gc_directive_;
 
   DISALLOW_COPY_AND_ASSIGN(DirectoryUpdateHandler);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_DIRECTORY_UPDATE_HANDLER_H_