dart2js: use IdGenerator for all id generation

pkg/compiler/lib/src/resolution/class_hierarchy.dart

 // Copyright (c) 2015, 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.
 
 library dart2js.resolution.class_hierarchy;
 
 import '../common.dart';
 import '../common/resolution.dart' show Feature;
 import '../compiler.dart' show Compiler;
 import '../core_types.dart' show CoreClasses, CoreTypes;
@@ skipping 281 matching lines @@
       link = link.tail;
     }
     doApplyMixinTo(element, supertype, checkMixinType(link.head));
     return element.computeType(resolution);
   }
 
   DartType applyMixin(DartType supertype, DartType mixinType, Node node) {
     String superName = supertype.name;
     String mixinName = mixinType.name;
     MixinApplicationElementX mixinApplication =
-        new UnnamedMixinApplicationElementX("${superName}+${mixinName}",
-            element.compilationUnit, compiler.getNextFreeId(), node);
+        new UnnamedMixinApplicationElementX(
+            "${superName}+${mixinName}",
+            element.compilationUnit,
+            compiler.idGenerator.getNextFreeId(),
+            node);
     // Create synthetic type variables for the mixin application.
     List<DartType> typeVariables = <DartType>[];
     int index = 0;
     for (TypeVariableType type in element.typeVariables) {
       TypeVariableElementX typeVariableElement = new TypeVariableElementX(
           type.name, mixinApplication, index, type.element.node);
       TypeVariableType typeVariable = new TypeVariableType(typeVariableElement);
       typeVariables.add(typeVariable);
       index++;
     }
@@ skipping 328 matching lines @@
     Identifier selector = node.selector.asIdentifier();
     var e = prefixElement.lookupLocalMember(selector.source);
     if (e == null || !e.impliesType) {
       reporter.reportErrorMessage(node.selector,
           MessageKind.CANNOT_RESOLVE_TYPE, {'typeName': node.selector});
       return;
     }
     loadSupertype(e, node);
   }
 }