Implement fetching, caching and retrieval of external policy data

chrome/browser/policy/cloud/cloud_external_data_manager.h

 // Copyright 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_POLICY_CLOUD_CLOUD_EXTERNAL_DATA_MANAGER_H_
 #define CHROME_BROWSER_POLICY_CLOUD_CLOUD_EXTERNAL_DATA_MANAGER_H_
 
 #include <map>
 #include <string>
 
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "chrome/browser/policy/external_data_manager.h"
 
+namespace net {
+class URLRequestContextGetter;
+}
+
 namespace policy {
 
+class CloudPolicyStore;
+
 // Downloads, verifies, caches and retrieves external data referenced by
 // policies.
 // This a common base class used by cloud policy implementations and mocks.
 class CloudExternalDataManager : public ExternalDataManager {
  public:
   struct MetadataEntry {
     MetadataEntry();
     MetadataEntry(const std::string& url, const std::string& hash);
 
+    bool operator!=(const MetadataEntry& other) const;
+
     std::string url;
     std::string hash;
   };
   // Maps from policy names to the metadata specifying the external data that
   // each of the policies references.
   typedef std::map<std::string, MetadataEntry> Metadata;
+
+  CloudExternalDataManager();
+  virtual ~CloudExternalDataManager();
+
+  // Sets the source of external data references to |policy_store|. The manager
+  // will start observing |policy_store| so that when external data references
+  // change, obsolete data can be deleted and new data can be downloaded. If the
+  // |policy_store| is destroyed before the manager, the connection must be
+  // severed first by calling SetPolicyStore(NULL).
+  virtual void SetPolicyStore(CloudPolicyStore* policy_store);
+
+  // Called by the |policy_store_| when policy changes.
+  virtual void OnPolicyStoreLoaded() = 0;
+
+  // Allows the manager to download external data by constructing URLFetchers
+  // from |request_context|.
+  virtual void Connect(
+      scoped_refptr<net::URLRequestContextGetter> request_context) = 0;
+
+  // Prevents further external data downloads and aborts any downloads currently
+  // in progress.
+  virtual void Disconnect() = 0;
+
+ protected:
+  CloudPolicyStore* policy_store_;  // Not owned.
+
+  base::WeakPtrFactory<CloudExternalDataManager> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(CloudExternalDataManager);
 };
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_CLOUD_CLOUD_EXTERNAL_DATA_MANAGER_H_