Refactor FileBasedPolicyProvider, introduce AsynchronousPolicyProvider.

chrome/browser/policy/asynchronous_policy_provider.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_PROVIDER_H_
+#define CHROME_BROWSER_POLICY_ASYNCHRONOUS_POLICY_PROVIDER_H_
+#pragma once
+
+#include "base/ref_counted.h"
+#include "base/weak_ptr.h"
+#include "chrome/browser/policy/configuration_policy_provider.h"
+
+namespace policy {
+
+class AsynchronousPolicyLoader;
+
+// Policy provider that loads policy asynchronously. Providers should subclass
+// from this class if loading the policy requires disk access or must for some
+// other reason be performed on the file thread. The actual logic for loading
+// policy is handled by a delegate passed at construction time.
+class AsynchronousPolicyProvider
+    : public ConfigurationPolicyProvider,
+      public base::SupportsWeakPtr<AsynchronousPolicyProvider> {
+ public:
+  // Must be implemented by subclasses of the asynchronous policy provider to
+  // provide the implementation details of how policy is loaded.
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    virtual DictionaryValue* Load() = 0;
+  };
+
+  // Assumes ownership of |loader|.
+  AsynchronousPolicyProvider(
+      const PolicyDefinitionList* policy_list,
+      scoped_refptr<AsynchronousPolicyLoader> loader);
+  virtual ~AsynchronousPolicyProvider();
+
+  // ConfigurationPolicyProvider implementation.
+  virtual bool Provide(ConfigurationPolicyStoreInterface* store);
+
+  // For tests to trigger reloads.
+  scoped_refptr<AsynchronousPolicyLoader> loader();
+
+ protected:
+  // The loader object used internally.
+  scoped_refptr<AsynchronousPolicyLoader> loader_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AsynchronousPolicyProvider);
+};
+
+}  // namespace policy
+
+#endif  // CHROME_BROWSER_POLICY_ASYNCHRONOUS_POLICY_PROVIDER_H_