Introduce faster swapping primitives.

src/ia32/codegen-ia32.h

Index: src/ia32/codegen-ia32.h
diff --git a/src/ia32/codegen-ia32.h b/src/ia32/codegen-ia32.h
index b3db0c42d3c895b3dd8142a7b2cef39188d53ec6..f527223a88bb28fc88a37561fb281de86cf7f0d5 100644
--- a/src/ia32/codegen-ia32.h
+++ b/src/ia32/codegen-ia32.h
@@ -636,6 +636,9 @@ class CodeGenerator: public AstVisitor {
   // Fast support for number to string.
   void GenerateNumberToString(ZoneList<Expression*>* args);
 
+  // Fast swapping of elements.
+  void GenerateSwapElements(ZoneList<Expression*>* args);
+
   // Fast call for custom callbacks.
   void GenerateCallFunction(ZoneList<Expression*>* args);