dns: Check if the cache is full during restoring from the old

During restoring from the old cache, RestoreFromListValue always traverses
all entries and sets the size of the entries to restore_size_.
The CL adds check if the cache is full during restoring for performance,
and sets restore_size_ to the number of cache entries that were restored.


Change-Id: I40f33f326e8aa92a2b8897879c652b8b3b41e825
Reviewed-on: https://chromium-review.googlesource.com/c/1369747
Commit-Queue: Paul Jensen <pauljensen@chromium.org>
Reviewed-by: Paul Jensen <pauljensen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615921}

net/dns/host_cache.cc

@@ -524,7 +524,15 @@ void HostCache::GetAsListValue(base::ListValue* entry_list,
 }
 
 bool HostCache::RestoreFromListValue(const base::ListValue& old_cache) {
+  // Reset the restore size to 0.
+  restore_size_ = 0;
+
   for (auto it = old_cache.begin(); it != old_cache.end(); it++) {
+    // If the cache is already full, don't bother prioritizing what to evict,
+    // just stop restoring.
+    if (size() == max_entries_)
+      break;
+
     const base::DictionaryValue* entry_dict;
     if (!it->GetAsDictionary(&entry_dict))
       return false;
@@ -634,16 +642,15 @@ bool HostCache::RestoreFromListValue(const base::ListValue& old_cache) {
             static_cast<HostResolverSource>(host_resolver_source));
 
     // If the key is already in the cache, assume it's more recent and don't
-    // replace the entry. If the cache is already full, don't bother
-    // prioritizing what to evict, just stop restoring.
+    // replace the entry.
     auto found = entries_.find(key);
-    if (found == entries_.end() && size() < max_entries_) {
+    if (found == entries_.end()) {
       AddEntry(key, Entry(error, address_list, std::move(text_records),
                           std::move(hostname_records), Entry::SOURCE_UNKNOWN,
                           expiration_time, network_changes_ - 1));
+      restore_size_++;
     }
   }
-  restore_size_ = old_cache.GetSize();
   return true;
 }
 

net/dns/host_cache_unittest.cc

@@ -733,7 +733,7 @@ TEST(HostCacheTest, SerializeAndDeserialize) {
   EXPECT_EQ(1u, result4->addresses().value().size());
   EXPECT_EQ(address_ipv4, result4->addresses().value().front().address());
 
-  EXPECT_EQ(3u, restored_cache.last_restore_size());
+  EXPECT_EQ(2u, restored_cache.last_restore_size());
 }
 
 TEST(HostCacheTest, SerializeAndDeserialize_Text) {