Improve array to string conversion.

src/codegen.h

Index: src/codegen.h
diff --git a/src/codegen.h b/src/codegen.h
index 3d14502d1161b98a28f2abb6a7acbfcc829e2ae6..6539e922a6a6651df72c8b30d1edb9def0aa0b50 100644
--- a/src/codegen.h
+++ b/src/codegen.h
@@ -104,6 +104,19 @@ class ElementsTransitionGenerator : public AllStatic {
   DISALLOW_COPY_AND_ASSIGN(ElementsTransitionGenerator);
 };
 
+
+class SeqStringSetCharGenerator : public AllStatic {
+ public:
+  static void Generate(MacroAssembler* masm,
+                       bool one_byte_string,
+                       Register string,
+                       Register index,
+                       Register value);
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SeqStringSetCharGenerator);
+};
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_CODEGEN_H_