Make policy errors available to display in about:policy.

chrome/browser/policy/configuration_policy_handler.h

+// 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.
+
+#ifndef CHROME_BROWSER_POLICY_CONFIGURATION_POLICY_HANDLER_H_
+#define CHROME_BROWSER_POLICY_CONFIGURATION_POLICY_HANDLER_H_
+#pragma once
+
+#include <vector>
+
+#include "base/basictypes.h"
+
+class PrefValueMap;
+
+namespace policy {
+
+class PolicyErrorMap;
+class PolicyMap;
+
+// An abstract super class that subclasses should implement to map policies to
+// their corresponding preferences, and to check whether the policies are valid.
+class ConfigurationPolicyHandler {
+ public:
+  typedef std::vector<ConfigurationPolicyHandler*> HandlerList;
+
+  ConfigurationPolicyHandler() {}
+  virtual ~ConfigurationPolicyHandler() {}
+
+  // Returns true if the policy settings handled by this
+  // ConfigurationPolicyHandler can be applied and false otherwise. Fills
+  // |errors| with error messages or warnings. |errors| may contain error
+  // messages even when |CheckPolicySettings()| returns true.
+  virtual bool CheckPolicySettings(const PolicyMap* policies,
+                                   PolicyErrorMap* errors) = 0;
+
+  // Processes the policies handled by this ConfigurationPolicyHandler and sets
+  // the appropriate preferences in |prefs|.
+  virtual void ApplyPolicySettings(const PolicyMap* policies,
+                                   PrefValueMap* prefs) = 0;
+
+  // Creates a new HandlerList with all the known handlers and returns it.
+  // The new list and its elements are owned by the caller.
+  static HandlerList* CreateHandlerList();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ConfigurationPolicyHandler);
+};
+
+}  // namespace policy
+
+#endif  // CHROME_BROWSER_POLICY_CONFIGURATION_POLICY_HANDLER_H_