Implement yield* (delegating yield)

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 10ae7de458d1653e36a7ab688dd15b9b68e297f4..e74cd461c978abf7d3c58b1b9747070c91090a2c 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -1982,6 +1982,18 @@ class Yield: public Expression {
   Kind yield_kind() const { return yield_kind_; }
   virtual int position() const { return pos_; }
 
+  // Delegating yield surrounds the "yield" in a "try/catch".  This index
+  // locates the catch handler in the handler table, and is equivalent to
+  // TryCatchStatement::index().
+  int index() const {
+    ASSERT(yield_kind() == DELEGATING);
+    return index_;
+  }
+  void set_index(int index) {
+    ASSERT(yield_kind() == DELEGATING);
+    index_ = index;
+  }
+
  protected:
   Yield(Isolate* isolate,
         Expression* generator_object,
@@ -1992,12 +2004,14 @@ class Yield: public Expression {
         generator_object_(generator_object),
         expression_(expression),
         yield_kind_(yield_kind),
+        index_(-1),
         pos_(pos) { }
 
  private:
   Expression* generator_object_;
   Expression* expression_;
   Kind yield_kind_;
+  int index_;
   int pos_;
 };