Certificate Transparency: Notify STH Observers of known STHs

net/cert/sth_distributor.h

 // Copyright 2016 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_CERT_STH_DISTRIBUTOR_H_
 #define NET_CERT_STH_DISTRIBUTOR_H_
 
+#include <vector>
+
 #include "base/observer_list.h"
 #include "net/base/net_export.h"
 #include "net/cert/sth_observer.h"
 #include "net/cert/sth_reporter.h"
 
 namespace net {
 
 namespace ct {
 
+struct SignedTreeHead;
+
 // A proxy for delegating new STH notifications to all registered
 // observers.
 // For each |observer| registered with RegisterObserver, the
 // NewSTHObserved method will be called whenever the STHDistributor's
 // NewSTHObserved method is invoked.
 class NET_EXPORT STHDistributor : public STHObserver, public STHReporter {
  public:
   STHDistributor();
   ~STHDistributor() override;
 
   // STHObserver implementation.
   void NewSTHObserved(const SignedTreeHead& sth) override;
 
   // STHReporter implementation
+  // Registers |observer| for new STH notifications. On registration,
+  // the |observer| will be notified of the latest STH for each log tha the
+  // STHDistributor has observed.
   void RegisterObserver(STHObserver* observer) override;
+
+  // Unregisters |observer|, which must have been previously
+  // registered via RegisterObserver()
   void UnregisterObserver(STHObserver* observer) override;
 
  private:
+  // STHs from logs, one for each log.
+  std::vector<SignedTreeHead> observed_sths_;
+
+  // The observers for new STH notifications.
   base::ObserverList<STHObserver> observer_list_;
 };
 
 }  // namespace ct
 
 }  // namespace net
 
 #endif  // NET_CERT_STH_DISTRIBUTOR_H_