Sync: Support multiple setup UIs.

components/sync_driver/sync_service.cc

Index: components/sync_driver/sync_service.cc
diff --git a/components/sync_driver/sync_service.cc b/components/sync_driver/sync_service.cc
index ab73a66a9f6780baef7710a45b6e1733dbb16ac3..ccff75fe2e8bf8ed891be3c3bac444ebfc8f5016 100644
--- a/components/sync_driver/sync_service.cc
+++ b/components/sync_driver/sync_service.cc
@@ -9,9 +9,31 @@
 
 namespace sync_driver {
 
+SyncSetupInProgressHandle::SyncSetupInProgressHandle(base::Closure on_destroy)
+    : on_destroy_(on_destroy) {}
+
+SyncSetupInProgressHandle::~SyncSetupInProgressHandle() {
+  on_destroy_.Run();
+}
+
 SyncService::SyncTokenStatus::SyncTokenStatus()
     : connection_status(syncer::CONNECTION_NOT_ATTEMPTED),
       last_get_token_error(GoogleServiceAuthError::AuthErrorNone()) {}
-SyncService::SyncTokenStatus::~SyncTokenStatus() {}
 
+std::unique_ptr<SyncSetupInProgressHandle>
+SyncService::GetSetupInProgressHandle() {
+  if (++outstanding_setup_in_progress_handles_ == 1)
+    SetSetupInProgress(true);
+
+  return std::unique_ptr<SyncSetupInProgressHandle>(
+      new SyncSetupInProgressHandle(
+          base::Bind(&SyncService::OnSetupInProgressHandleDestroyed,
+                     base::Unretained(this))));
 }
+
+void SyncService::OnSetupInProgressHandleDestroyed() {
+  if (--outstanding_setup_in_progress_handles_ == 0)
+    SetSetupInProgress(false);
+}
+
+}  // namespace sync_driver