Fix bug where generators got closed prematurely.

src/js/generator.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 18 matching lines @@
 function GeneratorObjectNext(value) {
   if (!IS_GENERATOR(this)) {
     throw MakeTypeError(kIncompatibleMethodReceiver,
                         '[Generator].prototype.next', this);
   }
 
   var continuation = %GeneratorGetContinuation(this);
   if (continuation > 0) {
     // Generator is suspended.
     DEBUG_PREPARE_STEP_IN_IF_STEPPING(this);
-    try {
-      return %_GeneratorNext(this, value);
-    } catch (e) {
-      %GeneratorClose(this);
-      throw e;
-    }
+    return %_GeneratorNext(this, value);
   } else if (continuation == 0) {
     // Generator is already closed.
     return { value: void 0, done: true };
   } else {
     // Generator is running.
     throw MakeTypeError(kGeneratorRunning);
   }
 }
 
 
 function GeneratorObjectThrow(exn) {
   if (!IS_GENERATOR(this)) {
     throw MakeTypeError(kIncompatibleMethodReceiver,
                         '[Generator].prototype.throw', this);
   }
 
   var continuation = %GeneratorGetContinuation(this);
   if (continuation > 0) {
     // Generator is suspended.
-    try {
-      return %_GeneratorThrow(this, exn);
-    } catch (e) {
-      %GeneratorClose(this);
-      throw e;
-    }
+    return %_GeneratorThrow(this, exn);
   } else if (continuation == 0) {
     // Generator is already closed.
     throw exn;
   } else {
     // Generator is running.
     throw MakeTypeError(kGeneratorRunning);
   }
 }
 
 // ----------------------------------------------------------------------------
@@ skipping 15 matching lines @@
 %AddNamedProperty(GeneratorObjectPrototype,
     toStringTagSymbol, "Generator", DONT_ENUM | READ_ONLY);
 %InternalSetPrototype(GeneratorFunctionPrototype, GlobalFunction.prototype);
 %AddNamedProperty(GeneratorFunctionPrototype,
     toStringTagSymbol, "GeneratorFunction", DONT_ENUM | READ_ONLY);
 %AddNamedProperty(GeneratorFunctionPrototype, "constructor",
     GeneratorFunction, DONT_ENUM | READ_ONLY);
 %InternalSetPrototype(GeneratorFunction, GlobalFunction);
 
 })