Use it=erase instead of old_it=it.

BUG=392576

Review URL: https://codereview.chromium.org/986413003

Cr-Commit-Position: refs/heads/master@{#319763}

net/http/http_server_properties_impl.cc

@@ -53,10 +53,10 @@ void HttpServerPropertiesImpl::InitializeAlternateProtocolServers(
   // Keep all the broken ones since those don't get persisted.
   for (AlternateProtocolMap::iterator it = alternate_protocol_map_.begin();
        it != alternate_protocol_map_.end();) {
-    AlternateProtocolMap::iterator old_it = it;
-    ++it;
-    if (!old_it->second.is_broken) {
-      alternate_protocol_map_.Erase(old_it);
+    if (it->second.is_broken) {
+      ++it;
+    } else {
+      it = alternate_protocol_map_.Erase(it);
     }
   }