Reporting: Add Observer interface to observe cache updates.

net/reporting/reporting_context.h

 // Copyright 2017 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 NET_REPORTING_REPORTING_CONTEXT_H_
 #define NET_REPORTING_REPORTING_CONTEXT_H_
 
 #include <memory>
 
+#include "base/observer_list.h"
 #include "base/time/time.h"
 #include "net/base/backoff_entry.h"
 #include "net/base/net_export.h"
 #include "net/reporting/reporting_policy.h"
 
 namespace base {
 class Clock;
 class TickClock;
 }  // namespace base
 
 namespace net {
 
 class ReportingCache;
 class ReportingDelegate;
 class ReportingDeliveryAgent;
 class ReportingEndpointManager;
+class ReportingObserver;
 class ReportingUploader;
 class URLRequestContext;
 
 // Contains the various internal classes that make up the Reporting system.
 // Wrapped by ReportingService, which provides the external interface.
 class NET_EXPORT ReportingContext {
  public:
   static std::unique_ptr<ReportingContext> Create(
       const ReportingPolicy& policy,
       std::unique_ptr<ReportingDelegate> delegate,
       URLRequestContext* request_context);
 
   ~ReportingContext();
 
   const ReportingPolicy& policy() { return policy_; }
   ReportingDelegate* delegate() { return delegate_.get(); }
 
   base::Clock* clock() { return clock_.get(); }
   base::TickClock* tick_clock() { return tick_clock_.get(); }
   ReportingUploader* uploader() { return uploader_.get(); }
 
   ReportingCache* cache() { return cache_.get(); }
   ReportingEndpointManager* endpoint_manager() {
     return endpoint_manager_.get();
   }
   ReportingDeliveryAgent* delivery_agent() { return delivery_agent_.get(); }
 
+  void AddObserver(ReportingObserver* observer);
+  void RemoveObserver(ReportingObserver* observer);
+
+  void NotifyCacheUpdated();
+
  protected:
   ReportingContext(const ReportingPolicy& policy,
                    std::unique_ptr<ReportingDelegate> delegate,
                    std::unique_ptr<base::Clock> clock,
                    std::unique_ptr<base::TickClock> tick_clock,
                    std::unique_ptr<ReportingUploader> uploader);
 
  private:
   ReportingPolicy policy_;
   std::unique_ptr<ReportingDelegate> delegate_;
 
   std::unique_ptr<base::Clock> clock_;
   std::unique_ptr<base::TickClock> tick_clock_;
   std::unique_ptr<ReportingUploader> uploader_;
 
+  base::ObserverList<ReportingObserver, /* check_empty= */ true> observers_;
+
   std::unique_ptr<ReportingCache> cache_;
 
   // |endpoint_manager_| must come after |tick_clock_| and |cache_|.
   std::unique_ptr<ReportingEndpointManager> endpoint_manager_;
 
   // |delivery_agent_| must come after |tick_clock_|, |uploader_|, |cache_|,
   // and |endpoint_manager_|.
   std::unique_ptr<ReportingDeliveryAgent> delivery_agent_;
 
   DISALLOW_COPY_AND_ASSIGN(ReportingContext);
 };
 
 }  // namespace net
 
 #endif  // NET_REPORTING_REPORTING_CONTEXT_H_