Fix the stack limits setting API so it is usable.

src/api.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 323 matching lines @@
 }
 
 
 ResourceConstraints::ResourceConstraints()
   : max_young_space_size_(0),
     max_old_space_size_(0),
     stack_limit_(NULL) { }
 
 
 bool SetResourceConstraints(ResourceConstraints* constraints) {
-  bool result = i::Heap::ConfigureHeap(constraints->max_young_space_size(),
-                                       constraints->max_old_space_size());
-  if (!result) return false;
+  int semispace_size = constraints->max_young_space_size();
+  int old_gen_size = constraints->max_old_space_size();
+  if (semispace_size != 0 || old_gen_size != 0) {
+    bool result = i::Heap::ConfigureHeap(semispace_size, old_gen_size);
+    if (!result) return false;
+  }
   if (constraints->stack_limit() != NULL) {
     uintptr_t limit = reinterpret_cast<uintptr_t>(constraints->stack_limit());
     i::StackGuard::SetStackLimit(limit);
   }
   return true;
 }
 
 
 i::Object** V8::GlobalizeReference(i::Object** obj) {
   if (IsDeadCheck("V8::Persistent::New")) return NULL;
@@ skipping 3409 matching lines @@
 
 
 char* HandleScopeImplementer::Iterate(ObjectVisitor* v, char* storage) {
   HandleScopeImplementer* thread_local =
       reinterpret_cast<HandleScopeImplementer*>(storage);
   thread_local->IterateThis(v);
   return storage + ArchiveSpacePerThread();
 }
 
 } }  // namespace v8::internal