unchanged:
--- protobuf-cleaned/src/google/protobuf/arenastring.cc	2015-12-30 13:21:46.000000000 -0800
+++ protobuf-patched/src/google/protobuf/arenastring.cc	2016-03-31 13:25:40.888006485 -0700
@@ -37,6 +37,20 @@
 namespace protobuf {
 namespace internal {
 
+::std::string* ArenaStringPtr::MutableNoArena(
+     const ::std::string* default_value) {
+  if (ptr_ == default_value) {
+    CreateInstanceNoArena(default_value);
+  }
+  return ptr_;
+}
+
+void ArenaStringPtr::DestroyNoArena(const ::std::string* default_value) {
+  if (ptr_ != default_value) {
+    delete ptr_;
+  }
+  ptr_ = NULL;
+}
 
 }  // namespace internal
 }  // namespace protobuf
only in patch2:
unchanged:
--- protobuf-cleaned/src/google/protobuf/arenastring.h	2015-12-30 13:21:46.000000000 -0800
+++ protobuf-patched/src/google/protobuf/arenastring.h	2016-03-31 13:25:40.888006485 -0700
@@ -214,12 +214,7 @@ struct LIBPROTOBUF_EXPORT ArenaStringPtr {
 
   inline const ::std::string& GetNoArena() const { return *ptr_; }
 
-  inline ::std::string* MutableNoArena(const ::std::string* default_value) {
-    if (ptr_ == default_value) {
-      CreateInstanceNoArena(default_value);
-    }
-    return ptr_;
-  }
+  ::std::string* MutableNoArena(const ::std::string* default_value);
 
   inline ::std::string* ReleaseNoArena(const ::std::string* default_value) {
     if (ptr_ == default_value) {
@@ -243,11 +238,7 @@ struct LIBPROTOBUF_EXPORT ArenaStringPtr {
     }
   }
 
-  inline void DestroyNoArena(const ::std::string* default_value) {
-    if (ptr_ != default_value) {
-      delete ptr_;
-    }
-  }
+  void DestroyNoArena(const ::std::string* default_value);
 
   inline void ClearToEmptyNoArena(const ::std::string* default_value) {
     if (ptr_ == default_value) {