Add hook for extension to check sync status.

chrome/browser/extensions/api/preferences_private/preferences_private_api.cc

+// Copyright 2013 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.
+
+#include "chrome/browser/extensions/api/preferences_private/preferences_private_api.h"
+
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/sync/profile_sync_service.h"
+#include "chrome/browser/sync/profile_sync_service_factory.h"
+#include "chrome/browser/sync/sync_prefs.h"
+#include "chrome/common/extensions/api/preferences_private.h"
+
+namespace extensions {
+
+namespace GetSyncCategoriesWithoutPassphrase =
+    api::preferences_private::GetSyncCategoriesWithoutPassphrase;
+
+PreferencesPrivateGetSyncCategoriesWithoutPassphraseFunction::
+PreferencesPrivateGetSyncCategoriesWithoutPassphraseFunction() {}
+
+PreferencesPrivateGetSyncCategoriesWithoutPassphraseFunction::
+~PreferencesPrivateGetSyncCategoriesWithoutPassphraseFunction() {}
+
+void
+PreferencesPrivateGetSyncCategoriesWithoutPassphraseFunction::OnStateChanged() {
+  ProfileSyncService* sync_service =
+      ProfileSyncServiceFactory::GetForProfile(GetProfile());
+  if (sync_service->sync_initialized()) {
+    sync_service->RemoveObserver(this);
+    RunImpl();
+    Release();  // Balanced in RunImpl().
+  }
+}
+
+bool PreferencesPrivateGetSyncCategoriesWithoutPassphraseFunction::RunImpl() {
+  ProfileSyncService* sync_service =
+      ProfileSyncServiceFactory::GetForProfile(GetProfile());
+  if (!sync_service->sync_initialized()) {
+    AddRef();  // Balanced in OnStateChanged().
+    sync_service->AddObserver(this);
+    return true;
+  }
+
+  syncer::ModelTypeSet result_set = syncer::UserSelectableTypes();
+
+  // Only include categories that are synced.
+  browser_sync::SyncPrefs sync_prefs(GetProfile()->GetPrefs());
+  if (!sync_prefs.HasKeepEverythingSynced()) {
+    result_set = syncer::Intersection(result_set,
+                                      sync_service->GetPreferredDataTypes());

[Nicolas Zea, 2013/12/19 00:23:59]

Do you want GetPreferred, or GetActive? Active is a subset of preferred, but
only includes those that are actually running (have fully started up and haven't
encountered an error). Depends on the use case.

[Rune Fevang, 2013/12/19 00:35:49]

The use case is "which types do the user want to sync" and not "which types are
currently synced", so I think GetPreferred is correct.

+  }
+  // Don't include encrypted categories.
+  result_set = syncer::Difference(result_set,
+                                  sync_service->GetEncryptedDataTypes());
+
+  std::vector<std::string> categories;
+  for (syncer::ModelTypeSet::Iterator it = result_set.First(); it.Good();
+      it.Inc()) {
+    categories.push_back(syncer::ModelTypeToString(it.Get()));
+  }
+
+  results_ = GetSyncCategoriesWithoutPassphrase::Results::Create(categories);
+  SendResponse(true);
+  return true;
+}
+
+}  // namespace extensions