third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/src/google/protobuf/generated_message_util.cc

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
 // https://developers.google.com/protocol-buffers/
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
@@ skipping 30 matching lines @@
 namespace protobuf {
 namespace internal {
 
 double Infinity() {
   return std::numeric_limits<double>::infinity();
 }
 double NaN() {
   return std::numeric_limits<double>::quiet_NaN();
 }
 
-const ::std::string* empty_string_;
+ExplicitlyConstructed< ::std::string> fixed_address_empty_string;
 GOOGLE_PROTOBUF_DECLARE_ONCE(empty_string_once_init_);
 
-void DeleteEmptyString() {
-  delete empty_string_;
-}
+void DeleteEmptyString() { fixed_address_empty_string.Shutdown(); }
 
 void InitEmptyString() {
-  empty_string_ = new string;
+  fixed_address_empty_string.DefaultConstruct();
   OnShutdown(&DeleteEmptyString);
 }
 
 const ::std::string& GetEmptyString() {
   ::google::protobuf::GoogleOnceInit(&empty_string_once_init_, &InitEmptyString);
   return GetEmptyStringAlreadyInited();
 }
 
 
 int StringSpaceUsedExcludingSelf(const string& str) {
   const void* start = &str;
   const void* end = &str + 1;
   if (start <= str.data() && str.data() < end) {
     // The string's data is stored inside the string object itself.
     return 0;
   } else {
     return str.capacity();
   }
 }
 
 
 
+void InitProtobufDefaults() {
+  GetEmptyString();
+}
+
 }  // namespace internal
 }  // namespace protobuf
 }  // namespace google