Add a TypeInformation abstraction in the inferrer, that holds information per element, to get rid o…

tests/compiler/dart2js/list_tracer_test.dart

 // Copyright (c) 2013, 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 'package:expect/expect.dart';
 import
     '../../../sdk/lib/_internal/compiler/implementation/types/types.dart'
     show ContainerTypeMask, TypeMask;
 
 import 'compiler_helper.dart';
@@ skipping 176 matching lines @@
 }
 
 void doTest(String allocation, {bool nullify}) {
   Uri uri = new Uri(scheme: 'source');
   var compiler = compilerFor(generateTest(allocation), uri);
   compiler.runCompiler(uri);
   var typesInferrer = compiler.typesTask.typesInferrer;
 
   checkType(String name, type) {
     var element = findElement(compiler, name);
-    ContainerTypeMask mask = typesInferrer.internal.typeOf[element];
+    ContainerTypeMask mask = typesInferrer.getTypeOfElement(element);
     if (nullify) type = type.nullable();
     Expect.equals(type, mask.elementType.simplify(compiler), name);
   }
 
   checkType('listInField', typesInferrer.numType);
   checkType('listPassedToMethod', typesInferrer.numType);
   checkType('listReturnedFromMethod', typesInferrer.numType);
   checkType('listUsedWithCascade', typesInferrer.numType);
   checkType('listUsedInClosure', typesInferrer.numType);
   checkType('listPassedToSelector', typesInferrer.numType);
@@ skipping 13 matching lines @@
   checkType('listReturnedFromClosure', typesInferrer.dynamicType);
   checkType('listUsedWithNonOkSelector', typesInferrer.dynamicType);
   checkType('listPassedAsOptionalParameter', typesInferrer.dynamicType);
   checkType('listPassedAsNamedParameter', typesInferrer.dynamicType);
 
   if (!allocation.contains('filled')) {
     checkType('listUnset', new TypeMask.nonNullEmpty());
     checkType('listOnlySetWithConstraint', new TypeMask.nonNullEmpty());
   }
 }