Add PersistenceDelegate to HostCache

net/dns/host_cache.h

Index: net/dns/host_cache.h
diff --git a/net/dns/host_cache.h b/net/dns/host_cache.h
index 39c95e4ff4c056424544c6ab63e2661fcdc80772..13042e3d569557ef3114752d7d95a8de06496525 100644
--- a/net/dns/host_cache.h
+++ b/net/dns/host_cache.h
@@ -124,6 +124,15 @@ class NET_EXPORT HostCache {
     int stale_hits_;
   };
 
+  // Interface for interacting with persistent storage, to be provided by the
+  // embedder. Does not include support for writes that must happen immediately.
+  class PersistenceDelegate {
+   public:
+    // Calling ScheduleWrite() signals that data has changed and should be
+    // written to persistent storage. The write might be delayed.
+    virtual void ScheduleWrite() = 0;
+  };
+
   using EntryMap = std::map<Key, Entry>;
   using EvictionCallback = base::Callback<void(const Key&, const Entry&)>;
 
@@ -158,6 +167,10 @@ class NET_EXPORT HostCache {
     eviction_callback_ = callback;
   }
 
+  void set_persistence_delegate(PersistenceDelegate* delegate) {
+    delegate_ = delegate;
+  }
+
   // Empties the cache.
   void clear();
 
@@ -196,7 +209,8 @@ class NET_EXPORT HostCache {
   void RecordSet(SetOutcome outcome,
                  base::TimeTicks now,
                  const Entry* old_entry,
-                 const Entry& new_entry);
+                 const Entry& new_entry,
+                 AddressListDeltaType delta);
   void RecordUpdateStale(AddressListDeltaType delta,
                          const EntryStaleness& stale);
   void RecordLookup(LookupOutcome outcome,
@@ -219,6 +233,8 @@ class NET_EXPORT HostCache {
   int network_changes_;
   EvictionCallback eviction_callback_;
 
+  PersistenceDelegate* delegate_;
+
   THREAD_CHECKER(thread_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(HostCache);