Fast string construct stub (ia32 only for now).

src/builtins.h

Index: src/builtins.h
diff --git a/src/builtins.h b/src/builtins.h
index 375e8f3f89051ed45b485b76f8f5efcf8c937c49..7e49f3133a6afe4b874bdfab1717532ac35b081f 100644
--- a/src/builtins.h
+++ b/src/builtins.h
@@ -117,7 +117,10 @@ enum BuiltinExtraArguments {
   V(FunctionApply,              BUILTIN, UNINITIALIZED)                   \
                                                                           \
   V(ArrayCode,                  BUILTIN, UNINITIALIZED)                   \
-  V(ArrayConstructCode,         BUILTIN, UNINITIALIZED)
+  V(ArrayConstructCode,         BUILTIN, UNINITIALIZED)                   \
+                                                                          \
+  V(StringConstructCode,        BUILTIN, UNINITIALIZED)
+
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
 // Define list of builtins used by the debugger implemented in assembly.
@@ -258,6 +261,8 @@ class Builtins : public AllStatic {
 
   static void Generate_ArrayCode(MacroAssembler* masm);
   static void Generate_ArrayConstructCode(MacroAssembler* masm);
+
+  static void Generate_StringConstructCode(MacroAssembler* masm);
 };
 
 } }  // namespace v8::internal