Replace symbol containing "prototype" with heap->prototype_symbol.

src/runtime.cc

 // Copyright 2012 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 2142 matching lines @@
   }
   return args[0];  // return TOS
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_FunctionSetReadOnlyPrototype) {
   NoHandleAllocation ha;
   RUNTIME_ASSERT(args.length() == 1);
   CONVERT_ARG_CHECKED(JSFunction, function, 0);
 
-  MaybeObject* maybe_name =
-      isolate->heap()->AllocateStringFromAscii(CStrVector("prototype"));
-  String* name;
-  if (!maybe_name->To(&name)) return maybe_name;
+  String* name = isolate->heap()->prototype_symbol();
 
   if (function->HasFastProperties()) {
     // Construct a new field descriptor with updated attributes.
     DescriptorArray* instance_desc = function->map()->instance_descriptors();
 
     int index = instance_desc->Search(name);
     ASSERT(index != DescriptorArray::kNotFound);
     PropertyDetails details = instance_desc->GetDetails(index);
 
     CallbacksDescriptor new_desc(name,
@@ skipping 11541 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal