Use Copy-on-write arrays for cached regexp results.

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 37b70110ccdee83439d74183958afccd9090328c..ce1bcf6a09fba36fdbf82e764259f4377b1d2e09 100644
--- a/src/ia32/codegen-ia32.h
+++ b/src/ia32/codegen-ia32.h
@@ -699,8 +699,14 @@ class CodeGenerator: public AstVisitor {
   // Support for direct calls from JavaScript to native RegExp code.
   void GenerateRegExpExec(ZoneList<Expression*>* args);
 
+  // Construct a RegExp exec result with two in-object properties.
   void GenerateRegExpConstructResult(ZoneList<Expression*>* args);
 
+  // Clone the result of a regexp function.
+  // Must be an object created by GenerateRegExpConstructResult with
+  // no extra properties.
+  void GenerateRegExpCloneResult(ZoneList<Expression*>* args);
+
   // Support for fast native caches.
   void GenerateGetFromCache(ZoneList<Expression*>* args);