Serialize and deserialize HostCache for persistence

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 37cf204e3ccb653aa3d642ad560a4ed361d7d5d9..c0ba45674d3890b27bffe2db661f7d70b60b3327 100644
--- a/net/dns/host_cache.h
+++ b/net/dns/host_cache.h
@@ -8,6 +8,7 @@
 #include <stddef.h>
 
 #include <functional>
+#include <map>
 #include <memory>
 #include <string>
 #include <tuple>
@@ -22,6 +23,10 @@
 #include "net/base/net_export.h"
 #include "net/dns/dns_util.h"
 
+namespace base {
+class ListValue;
+}
+
 namespace net {
 
 // Cache used by HostResolver to map hostnames to their resolved result.
@@ -90,6 +95,11 @@ class NET_EXPORT HostCache : NON_EXPORTED_BASE(public base::NonThreadSafe) {
           base::TimeDelta ttl,
           int network_changes);
 
+    Entry(int error,
+          const AddressList& addresses,
+          base::TimeTicks expires,
+          int network_changes);
+
     int total_hits() const { return total_hits_; }
     int stale_hits() const { return stale_hits_; }
 
@@ -155,6 +165,14 @@ class NET_EXPORT HostCache : NON_EXPORTED_BASE(public base::NonThreadSafe) {
   void ClearForHosts(
       const base::Callback<bool(const std::string&)>& host_filter);
 
+  // Returns the contents of the cache represented as a base::ListValue for
+  // serialization.
+  std::unique_ptr<base::ListValue> GetAsListValue(bool include_staleness) const;
+  // Takes a base::ListValue representing cache entries and stores them in the
+  // cache, skipping any that already have entries. Returns true on success,
+  // false on failure.
+  bool RestoreFromListValue(base::ListValue& old_cache);
+
   // Returns the number of entries in the cache.
   size_t size() const;
 
@@ -191,6 +209,8 @@ class NET_EXPORT HostCache : NON_EXPORTED_BASE(public base::NonThreadSafe) {
   bool caching_is_disabled() const { return max_entries_ == 0; }
 
   void EvictOneEntry(base::TimeTicks now);
+  // Helper to insert an Entry into the cache.
+  void AddEntry(const Key& key, const Entry& entry);
 
   // Map from hostname (presumably in lowercase canonicalized format) to
   // a resolved result entry.