Ensure that collectedClasses always contains a [globalObject, descriptor] pair.

pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter;
 
 
 class OldEmitter implements Emitter {
   final Compiler compiler;
   final CodeEmitterTask task;
@@ skipping 1176 matching lines @@
     String fieldNamesProperty = FIELD_NAMES_PROPERTY_NAME;
     bool hasIsolateSupport = compiler.hasIsolateSupport;
     jsAst.Node fieldNamesArray =
         hasIsolateSupport ? js.stringArray(fields) : new jsAst.LiteralNull();
 
     cspPrecompiledFunctionFor(outputUnit).add(js.statement(r'''
         {
           #constructorName.builtin$cls = #constructorNameString;
           if (!"name" in #constructorName)
               #constructorName.name = #constructorNameString;
-          $desc = $collectedClasses.#constructorName;
-          if ($desc instanceof Array) $desc = $desc[1];
+          $desc = $collectedClasses.#constructorName[1];
           #constructorName.prototype = $desc;
           ''' /* next string is not a raw string */ '''
           if (#hasIsolateSupport) {
             #constructorName.$fieldNamesProperty = #fieldNamesArray;
           }
         }''',
         {"constructorName": constructorName,
          "constructorNameString": js.string(constructorName),
          "hasIsolateSupport": hasIsolateSupport,
          "fieldNamesArray": fieldNamesArray}));
@@ skipping 813 matching lines @@
     for (Element element in compiler.enqueuer.codegen.newlyEnqueuedElements) {
       if (element.isInstanceMember) {
         cachedClassBuilders.remove(element.enclosingClass);
 
         nativeEmitter.cachedBuilders.remove(element.enclosingClass);
 
       }
     }
   }
 }