Don't compile functions in a context the caller doesn't have access to

src/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 62 matching lines @@
     throw MakeTypeError(kGeneratorRunning);
   }
 }
 
 
 function GeneratorFunctionConstructor(arg1) {  // length == 1
   var source = NewFunctionString(arguments, 'function*');
   var global_proxy = %GlobalProxy(GeneratorFunctionConstructor);
   // Compile the string in the constructor and not a helper so that errors
   // appear to come from here.
-  var f = %_CallFunction(global_proxy, %CompileString(source, true));
+  var f = %CompileString(source, true);
+  if (!IS_FUNCTION(f)) return f;
+  f = %_CallFunction(global_proxy, f);
   %FunctionMarkNameShouldPrintAsAnonymous(f);
   return f;
 }
 
 // ----------------------------------------------------------------------------
 
 // Both Runtime_GeneratorNext and Runtime_GeneratorThrow are supported by
 // neither Crankshaft nor TurboFan, disable optimization of wrappers here.
 %NeverOptimizeFunction(GeneratorObjectNext);
 %NeverOptimizeFunction(GeneratorObjectThrow);
@@ skipping 11 matching lines @@
     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);
 %SetCode(GeneratorFunction, GeneratorFunctionConstructor);
 
 })