Introduce read buffer for external strings when using charAt (ia32).

src/runtime.cc

 // Copyright 2011 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 2238 matching lines @@
   Object* flat;
   { MaybeObject* maybe_flat = subject->TryFlatten();
     if (!maybe_flat->ToObject(&flat)) return maybe_flat;
   }
   subject = String::cast(flat);
 
   if (i >= static_cast<uint32_t>(subject->length())) {
     return isolate->heap()->nan_value();
   }
 
-  return Smi::FromInt(subject->Get(i));
+  return Smi::FromInt(subject->Get(i, String::UPDATE_EXTERNAL_STRING_BUFFER));
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_CharFromCode) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);
   return CharFromCode(isolate, args[0]);
 }
 
 
@@ skipping 11267 matching lines @@
   } else {
     // 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);
   }
 }
 
 
 } }  // namespace v8::internal