Merge CoreTypes and CoreClasses into CommonElements.

tests/compiler/dart2js/resolver_test.dart

 // Copyright (c) 2012, 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.
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/constants/expressions.dart';
@@ skipping 146 matching lines @@
       index++;
     }
     Expect.equals(index, expectedElements.length);
   }
 
   return Future.wait([
     MockCompiler.create((MockCompiler compiler) {
       ResolverVisitor visitor = compiler.resolverVisitor();
       compiler.parseScript('class Foo<T, U> {}');
       ClassElement foo = compiler.mainApp.find('Foo');
-      matchResolvedTypes(visitor, 'Foo<int, String> x;', 'Foo',
-          [compiler.coreClasses.intClass, compiler.coreClasses.stringClass]);
+      matchResolvedTypes(visitor, 'Foo<int, String> x;', 'Foo', [
+        compiler.commonElements.intClass,
+        compiler.commonElements.stringClass
+      ]);
       matchResolvedTypes(visitor, 'Foo<Foo, Foo> x;', 'Foo', [foo, foo]);
     }),
     MockCompiler.create((MockCompiler compiler) {
       compiler.parseScript('class Foo<T, U> {}');
       compiler.resolveStatement('Foo<notype, int> x;');
       DiagnosticCollector collector = compiler.diagnosticCollector;
       Expect.equals(1, collector.warnings.length);
       Expect.equals(MessageKind.CANNOT_RESOLVE_TYPE,
           collector.warnings.first.message.kind);
       Expect.equals(0, collector.errors.length);
@@ skipping 1355 matching lines @@
       functionName: 'm');
   check(
       '''
     class A {
       m() => () => await - 3;
     }
     main() => new A().m();
   ''',
       className: 'A');
 }