[Sync] Make ModelSafeWorker a true interface

chrome/browser/sync/test/engine/fake_model_worker.cc

+// Copyright (c) 2011 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/sync/test/engine/fake_model_worker.h"
+
+namespace browser_sync {
+
+FakeModelWorker::FakeModelWorker(ModelSafeGroup group) : group_(group) {}
+
+FakeModelWorker::~FakeModelWorker() {
+  // We may need to relax this is FakeModelWorker is used in a
+  // multi-threaded test; since ModelSafeWorkers are
+  // RefCountedThreadSafe, they could theoretically be destroyed from
+  // a different thread.
+  DCHECK(non_thread_safe_.CalledOnValidThread());
+}
+
+UnrecoverableErrorInfo FakeModelWorker::DoWorkAndWaitUntilDone(
+    const WorkCallback& work) {
+  DCHECK(non_thread_safe_.CalledOnValidThread());
+  // Simply do the work on the current thread.
+  return work.Run();
+}
+
+ModelSafeGroup FakeModelWorker::GetModelSafeGroup() {
+  DCHECK(non_thread_safe_.CalledOnValidThread());
+  return group_;
+}
+
+}  // namespace browser_sync