Do not persist HttpServerProperties to disk that often.

net/http/http_server_properties.h

Index: net/http/http_server_properties.h
diff --git a/net/http/http_server_properties.h b/net/http/http_server_properties.h
index 5acc682e6f0d93b3a52b9c8fd33cb28dbe91af54..7d3e6eed83a08760bb5ce8ec375381f67f00f312 100644
--- a/net/http/http_server_properties.h
+++ b/net/http/http_server_properties.h
@@ -265,7 +265,8 @@ class NET_EXPORT HttpServerProperties {
   // Set a single alternative service for |origin|.  Previous alternative
   // services for |origin| are discarded.
   // |alternative_service.host| may be empty.
-  // Return true if |alternative_service_map_| is changed.
+  // Return true if |alternative_service_map_| has changed significantly enough
+  // that it should be persisted to disk.
   virtual bool SetAlternativeService(
       const url::SchemeHostPort& origin,
       const AlternativeService& alternative_service,
@@ -274,7 +275,9 @@ class NET_EXPORT HttpServerProperties {
   // Set alternative services for |origin|.  Previous alternative services for
   // |origin| are discarded.
   // Hostnames in |alternative_service_info_vector| may be empty.
-  // Return true if |alternative_service_map_| is changed.
+  // |alternative_service_info_vector| may be empty.
+  // Return true if |alternative_service_map_| has changed significantly enough
+  // that it should be persisted to disk.
   virtual bool SetAlternativeServices(
       const url::SchemeHostPort& origin,
       const AlternativeServiceInfoVector& alternative_service_info_vector) = 0;