Refactor FileBasedPolicyProvider, introduce AsynchronousPolicyProvider.

chrome/browser/policy/asynchronous_policy_loader.h

+// Copyright (c) 2010 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_POLICY_ASYNCHRONOUS_POLICY_LOADER_H_
+#define CHROME_BROWSER_POLICY_ASYNCHRONOUS_POLICY_LOADER_H_
+#pragma once
+
+#include "base/ref_counted.h"
+#include "base/values.h"
+#include "chrome/browser/policy/asynchronous_policy_provider.h"
+
+namespace policy {
+
+class ConfigurationPolicyProvider;
+
+// Used by the implementation of asynchronous policy provider to managed the

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

to manage

[danno, 2010/12/06 14:05:12]

Done.

+// tasks on the file thread that do the heavy lifting of loading policies on the

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

"on the file thread" twice?

[danno, 2010/12/06 14:05:12]

Done.

+// file thread.
+class AsynchronousPolicyLoader
+    : public base::RefCountedThreadSafe<AsynchronousPolicyLoader> {
+ public:
+  explicit AsynchronousPolicyLoader(
+      AsynchronousPolicyProvider::Delegate* delegate);
+
+  // Triggers initial policy load and schedules fallback reload.

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

In the base implementation, it doesn't schedule fallback reload.

[danno, 2010/12/06 14:05:12]

Done.

+  virtual void Init();
+
+  // Reloads policy, sending notification of changes if necessary. Must be
+  // called on the file thread.
+  virtual void Reload();
+
+  // Stops any pending reload tasks.
+  virtual void Stop();
+
+  // Associates a provider with the loader to allow the loader to notify the
+  // provider when policy changes.
+  void SetProvider(base::WeakPtr<AsynchronousPolicyProvider> provider);

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

If there is SetProvider(), you don't need to pass a WeakPtr, since you can just
do SetProvider(NULL) when the provider goes away.

What's the plan for the next iteration? Remove this? If so, please put a TODO.

[danno, 2010/12/06 14:05:12]

Done. TODO already in .cc file.

+
+  const DictionaryValue* policy() const { return policy_.get(); }
+
+ protected:
+  friend class UpdatePolicyTask;
+
+  // AsynchronousPolicyLoader objects should only be deleted by
+  // RefCountedThreadSafe.
+  friend class base::RefCountedThreadSafe<AsynchronousPolicyLoader>;
+  virtual ~AsynchronousPolicyLoader() {}
+
+  // Schedules a call to UpdatePolicy on the ui thread. Must be called on the
+  // FILE thread.
+  void PostUpdatePolicyTask(DictionaryValue* new_policy);
+
+  // Replaces the existing policy to value map with a new once, sending

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

s/once/one/

[danno, 2010/12/06 14:05:12]

Done.

+  // notification to the provider if there is a policy change. Must be called on
+  // the ui thread.

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

s/ui/UI/ (you say FILE thread above)

[danno, 2010/12/06 14:05:12]

Done.

+  void UpdatePolicy(DictionaryValue* new_policy);
+
+  AsynchronousPolicyProvider::Delegate* delegate() {
+    return delegate_.get();
+  }
+
+ private:
+  friend class AsynchronousPolicyLoaderTest;
+
+  // Provides the low-level mechanics for loading policy.
+  scoped_ptr<AsynchronousPolicyProvider::Delegate> delegate_;
+
+  // Current policy.
+  scoped_ptr<DictionaryValue> policy_;
+
+  // The provider this loader is associated with. Access only on the thread that
+  // called the constructor. See |origin_loop_| below.
+  base::WeakPtr<AsynchronousPolicyProvider> provider_;
+
+  // The message loop on which this object was constructed and |provider_|
+  // received on. Recorded so we can call back into the non thread safe provider
+  // to fire the notification.
+  MessageLoop* origin_loop_;

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

Do we still need this? If yes, the comment above concerning the UI thread is not
precise.

[danno, 2010/12/06 14:05:12]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(AsynchronousPolicyLoader);
+};
+
+}  // namespace policy
+
+#endif  // CHROME_BROWSER_POLICY_ASYNCHRONOUS_POLICY_LOADER_H_