Introduce IEImporterTestRegistryOverrider to be able to override the registry for a test and flag t…

chrome/browser/importer/ie_importer_test_registry_overrider_win.h

+// Copyright (c) 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.
+
+#ifndef CHROME_BROWSER_IMPORTER_IE_IMPORTER_TEST_REGISTRY_OVERRIDER_WIN_H_
+#define CHROME_BROWSER_IMPORTER_IE_IMPORTER_TEST_REGISTRY_OVERRIDER_WIN_H_
+
+#include "base/basictypes.h"
+#include "base/lazy_instance.h"
+#include "base/string16.h"
+#include "base/synchronization/lock.h"
+
+// A helper class to override HKEY_CURRENT_USER to point to a test key from this
+// process' point of view. Uses a random guid as a subkey for the override in
+// order for multiple tests to be able to use this functionality in parallel.
+// Also provides functionality (via an environment variable) to let child
+// processes check whether they should also override. This class is thread-safe.
+// Always unsets any existing override upon being deleted.
+class IEImporterTestRegistryOverrider {
+ public:
+  IEImporterTestRegistryOverrider();
+
+  // Unsets any existing registry override and deletes the temporary registry
+  // key if |override_initiated_|.
+  ~IEImporterTestRegistryOverrider();
+
+  // Calls StartRegistryOverride() and sets an environment variable so that
+  // future calls to StartRegistryOverrideIfNeeded() from child processes also
+  // result in an overriden HKEY_CURRENT_USER hive. This method should only be
+  // called once across all processes.
+  // Returns false on unexpected failure.
+  bool SetRegistryOverride();
+
+  // Calls StartRegistryOverride() if the environment was set by a parent
+  // process via SetRegistryOverride().
+  // Returns false on unexpected failure.
+  bool StartRegistryOverrideIfNeeded();
+
+ private:
+  // Overrides HKCU to point to a test key (ending with |subkey|) from this
+  // process' point of view. Re-applies the override without taking ownership if
+  // |override_active_in_process_|.
+  // Returns false on unexpected failure.
+  bool StartRegistryOverride(const base::string16& subkey);
+
+  // Whether this object started an override for the current process (and thus
+  // will be responsible for unsetting it when done).
+  bool override_performed_;
+
+  // Whether this object is the one that initiated the override via
+  // SetRegistryOverride() (and thus will be the one responsible for deleting
+  // the temporary key when done).
+  bool override_initiated_;
+
+  // Whether a registry override was initiated in the current process.
+  static bool override_active_in_process_;
+
+  // This lock should be held before accessing this class' static data and any
+  // of its objects' members.
+  static base::LazyInstance<base::Lock>::Leaky lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(IEImporterTestRegistryOverrider);
+};
+
+#endif  // CHROME_BROWSER_IMPORTER_IE_IMPORTER_TEST_REGISTRY_OVERRIDER_WIN_H_