DNS: Let requests specify a callback for future cache hits

net/dns/host_resolver_impl.h

Index: net/dns/host_resolver_impl.h
diff --git a/net/dns/host_resolver_impl.h b/net/dns/host_resolver_impl.h
index 9ab01ca03ea1a6d3ea4a828249d546537a127f4f..691d8faee2a02b9624495e849dd18b09cbe2c8a6 100644
--- a/net/dns/host_resolver_impl.h
+++ b/net/dns/host_resolver_impl.h
@@ -297,6 +297,13 @@ class NET_EXPORT HostResolverImpl
   // and resulted in |net_error|.
   void OnDnsTaskResolve(int net_error);
 
+  void OnCacheEntryEvicted(const HostCache::Key& key,
+                           const HostCache::Entry& entry);
+  void ClearCacheHitCallbacks(const HostCache::Key& key);
+  void MaybeAddCacheHitCallback(const HostCache::Key& key,
+                                const RequestInfo& info);
+  void RunCacheHitCallbacks(const HostCache::Key& key, const RequestInfo& info);
+
   // Allows the tests to catch slots leaking out of the dispatcher.  One
   // HostResolverImpl::Job could occupy multiple PrioritizedDispatcher job
   // slots.
@@ -353,6 +360,9 @@ class NET_EXPORT HostResolverImpl
   // tasks, but can be overridden for tests.
   scoped_refptr<base::TaskRunner> worker_task_runner_;
 
+  std::map<const HostCache::Key, std::vector<RequestInfo::CacheHitCallback>>
+      cache_hit_callbacks_;
+
   base::WeakPtrFactory<HostResolverImpl> weak_ptr_factory_;
 
   base::WeakPtrFactory<HostResolverImpl> probe_weak_ptr_factory_;