Remove experimental ExternalSymbolCallback feature. This is not needed...

src/heap-inl.h

 // Copyright 2006-2008 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 23 matching lines @@
 namespace v8 { namespace internal {
 
 int Heap::MaxHeapObjectSize() {
   return Page::kMaxHeapObjectSize;
 }
 
 
 Object* Heap::AllocateSymbol(Vector<const char> str,
                              int chars,
                              uint32_t length_field) {
-  if (global_external_symbol_callback_) {
-    return AllocateExternalSymbol(str, chars);
-  }
   unibrow::Utf8InputBuffer<> buffer(str.start(),
                                     static_cast<unsigned>(str.length()));
   return AllocateInternalSymbol(&buffer, chars, length_field);
 }
 
 
 Object* Heap::AllocateRaw(int size_in_bytes,
                           AllocationSpace space,
                           AllocationSpace retry_space) {
   ASSERT(allocation_allowed_ && gc_state_ == NOT_IN_GC);
@@ skipping 218 matching lines @@
   allocation_allowed_ = new_state;
   return old;
 }
 
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_