Don't internalize names that are array indexes since they aren't used for lookup (the index is)

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 235faa3c3998dc1f9e22db7948927177d51abf92..22f6b0975498b975b53f0bc9a58cefd2cea1be1b 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -2229,9 +2229,6 @@ Handle<String> Factory::NumberToString(Handle<Object> number,
   // We tenure the allocated string since it is referenced from the
   // number-string cache which lives in the old space.
   Handle<String> js_string = NewStringFromAsciiChecked(str, TENURED);
-  // Make sure the string cached in the number cache is also the internalized
-  // version of the same string.
-  js_string = InternalizeString(js_string);
   SetNumberStringCache(number, js_string);
   return js_string;
 }