Fix symbol-named function template properties in the API

src/apinatives.js

 // Copyright 2006-2008 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.
 
 "use strict";
 
 // This file contains infrastructure used by the API.  See
 // v8natives.js for an explanation of these files are processed and
 // loaded.
 
@@ skipping 54 matching lines @@
 
         var parent = %GetTemplateField(data, kApiParentTemplateOffset);
         // Note: Do not directly use a function template as a condition, our
         // internal ToBoolean doesn't handle that!
         if (typeof parent !== 'undefined') {
           var parent_fun = Instantiate(parent);
           %InternalSetPrototype(prototype, parent_fun.prototype);
         }
       }
       var fun = %CreateApiFunction(data, prototype);
-      if (name) %FunctionSetName(fun, name);
+      if (IS_STRING(name)) %FunctionSetName(fun, name);
       var doNotCache = flags & (1 << kDoNotCacheBit);
       if (!doNotCache) cache[serialNumber] = fun;
       ConfigureTemplateInstance(fun, data);
       if (doNotCache) return fun;
     } catch (e) {
       cache[serialNumber] = kUninitialized;
       throw e;
     }
   }
   return cache[serialNumber];
@@ skipping 24 matching lines @@
         %DefineApiAccessorProperty(obj, name, getter, setter, attribute);
       } else {
         throw "Bad properties array";
       }
       i += length + 1;
     }
   } finally {
     if (requires_access_checks) %EnableAccessChecks(obj);
   }
 }