sync: Refactor migration integration tests

chrome/browser/sync/test/integration/migration_waiter.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 CHROME_BROWSER_SYNC_TEST_INTEGRATION_MIGRATION_WAITER_H_
+#define CHROME_BROWSER_SYNC_TEST_INTEGRATION_MIGRATION_WAITER_H_
+
+#include "base/macros.h"
+#include "chrome/browser/sync/test/integration/status_change_checker.h"
+#include "sync/internal_api/public/base/model_type.h"
+
+class MigrationWatcher;
+
+// Helper class that checks if the sync backend has successfully completed
+// migration for a set of data types.
+//
+// Collaborates with the MigrationWatcher, defined above.
+class MigrationWaiter : public StatusChangeChecker {
+ public:
+  // Initialize a waiter that will wait until |watcher|'s migrated types
+  // match the provided |exptected_types|.
+  MigrationWaiter(syncer::ModelTypeSet expected_types,
+                  MigrationWatcher* watcher);
+
+  virtual ~MigrationWaiter();
+
+  // Implementation of StatusChangeChecker.
+  virtual bool IsExitConditionSatisfied() OVERRIDE;
+  virtual std::string GetDebugMessage() const OVERRIDE;
+
+  // Function to trigger the waiting.
+  void Wait();
+
+  // Callback invoked by our associated waiter when migration state changes.
+  void OnMigrationStateChange();
+
+ private:
+  // The MigrationWatcher we're observering.
+  MigrationWatcher* const watcher_;

[David Abrahams, 2014/08/22 18:54:41]

Nit: Feels a little weird that a Watcher has a Waiter and a Waiter has a
Watcher. But I can deal with it if it makes splitting the classses much simpler.

+
+  // The set of data types that are expected to eventually undergo migration.
+  const syncer::ModelTypeSet expected_types_;
+
+  DISALLOW_COPY_AND_ASSIGN(MigrationWaiter);
+};
+
+#endif  // CHROME_BROWSER_SYNC_TEST_INTEGRATION_MIGRATION_WAITER_H_