Move WorldImpact to universe/world_impact.dart

pkg/compiler/lib/src/common/backend_api.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.
 
 library dart2js.backend_api;
 
 import 'dart:async' show Future;
 
 import '../common.dart';
 import '../compiler.dart' show
@@ skipping 13 matching lines @@
 import '../elements/elements.dart' show
     ClassElement,
     ConstructorElement,
     Element,
     FunctionElement,
     LibraryElement,
     MetadataAnnotation;
 import '../enqueue.dart' show
     Enqueuer,
     CodegenEnqueuer,
-    ResolutionEnqueuer,
-    WorldImpact;
+    ResolutionEnqueuer;
 import '../io/code_output.dart' show
     CodeBuffer;
 import '../io/source_information.dart' show
     SourceInformationStrategy;
 import '../js_backend/js_backend.dart' as js_backend show
     JavaScriptBackend;
 import '../library_loader.dart' show
     LibraryLoader,
     LoadedLibraries;
 import '../native/native.dart' as native show
     NativeEnqueuer;
 import '../patch_parser.dart' show
     checkNativeAnnotation;
 import '../resolution/tree_elements.dart' show
     TreeElements;
 import '../tree/tree.dart' show
     Node,
     Send;
 import '../universe/call_structure.dart' show
     CallStructure;
+import '../universe/world_impact.dart' show
+    WorldImpact;
 
 import 'codegen.dart' show
     CodegenWorkItem;
 import 'registry.dart' show
     Registry;
 import 'resolution.dart' show
     ResolutionCallbacks;
 import 'tasks.dart' show
     CompilerTask;
 import 'work.dart' show
@@ skipping 326 matching lines @@
   /// Returns the constant expression of [node], or `null` if [node] is not
   /// a constant expression.
   ConstantExpression getConstant(Node node);
 
   /// Registers [type] as instantiated.
   void registerInstantiatedType(InterfaceType type);
 
   /// Resolves [typeName] to a type in the context of [node].
   DartType resolveTypeFromString(Node node, String typeName);
 }