Allow compiling with strict aliasing enabled on GCC 4.4.

src/heap.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 4006 matching lines @@
     ExternalStringTable::Iterate(v);
   }
   v->Synchronize("external_string_table");
 }
 
 
 void Heap::IterateStrongRoots(ObjectVisitor* v, VisitMode mode) {
   v->VisitPointers(&roots_[0], &roots_[kStrongRootListLength]);
   v->Synchronize("strong_root_list");
 
-  v->VisitPointer(BitCast<Object**, String**>(&hidden_symbol_));
+  v->VisitPointer(BitCast<Object**>(&hidden_symbol_));
   v->Synchronize("symbol");
 
   Bootstrapper::Iterate(v);
   v->Synchronize("bootstrapper");
   Top::Iterate(v);
   v->Synchronize("top");
   Relocatable::Iterate(v);
   v->Synchronize("relocatable");
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
@@ skipping 988 matching lines @@
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
 List<Object*> ExternalStringTable::new_space_strings_;
 List<Object*> ExternalStringTable::old_space_strings_;
 
 } }  // namespace v8::internal