components: add wifi_sync component

components/wifi_sync/wifi_credential_syncable_service.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_WIFI_SYNC_WIFI_CREDENTIAL_SYNCABLE_SERVICE_H_
+#define COMPONENTS_WIFI_SYNC_WIFI_CREDENTIAL_SYNCABLE_SERVICE_H_
+
+#include <stdint.h>
+
+#include <set>
+#include <utility>

[erikwright (departed), 2014/12/08 21:21:36]

double-check all the includes here.

[mukesh agrawal, 2014/12/09 01:41:11]

Done.

+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "sync/api/sync_change_processor.h"
+#include "sync/api/sync_error_factory.h"
+#include "sync/api/syncable_service.h"
+
+namespace wifi_sync {
+
+// KeyedService that synchronizes WiFi credentials between local settings,
+// and Chrome Sync.
+//
+// This service does not necessarily own the storage for WiFi
+// credentials. In particular, on ChromeOS, WiFi credential storage is
+// managed by the ChromeOS connection manager ("Shill").
+class WifiCredentialSyncableService
+    : public syncer::SyncableService, public KeyedService {
+ public:
+  WifiCredentialSyncableService();
+  ~WifiCredentialSyncableService() override;
+
+  // syncer::SyncableService implementation.
+  syncer::SyncMergeResult MergeDataAndStartSyncing(
+      syncer::ModelType type,
+      const syncer::SyncDataList& initial_sync_data,
+      scoped_ptr<syncer::SyncChangeProcessor> sync_processor,
+      scoped_ptr<syncer::SyncErrorFactory> error_handler) override;
+  void StopSyncing(syncer::ModelType type) override;
+  syncer::SyncDataList GetAllSyncData(syncer::ModelType type) const override;
+  syncer::SyncError ProcessSyncChanges(
+      const tracked_objects::Location& caller_location,
+      const syncer::SyncChangeList& change_list) override;
+
+ private:
+  // The syncer::ModelType that this SyncableService processes and
+  // generates updates for.
+  static const syncer::ModelType kModelType;
+
+  // Our ThreadChecker instance. Used to ensure that all calls to an
+  // instance of this class are made from the same thread.
+  const base::ThreadChecker thread_checker_;

[erikwright (departed), 2014/12/08 21:21:36]

Is this a common convention for "SyncableService" implementations? Unless I'm
mistaken, all keyed services are expected to be used exclusively on the UI
thread, and I don't think we typically go to the trouble of asserting this.

Basically, we wouldn't add a ThreadChecker to every class in Chrome (even though
most are single-threaded) so I want to understand what source of risk warrants
adding one here.

[mukesh agrawal, 2014/12/09 01:41:11]

After checking the existing code, I see that, of the 21 SyncableService
subclasses, only HistoryService and ThemeSyncableService have a ThreadChecker.
HistoryService probably needs the ThreadChecker because HistoryService creates
its own thread.

Since ThreadChecker isn't a common requirement of SyncableServices, I've removed
the ThreadChecker from WifiCredentialSyncableService.

+  // Our SyncChangeProcessor instance. Used to push changes into
+  // Chrome Sync.
+  scoped_ptr<syncer::SyncChangeProcessor> sync_processor_;
+
+  DISALLOW_COPY_AND_ASSIGN(WifiCredentialSyncableService);
+};
+
+}  // namespace wifi_sync
+
+#endif  // COMPONENTS_WIFI_SYNC_WIFI_CREDENTIAL_SYNCABLE_SERVICE_H_