Move ResolutionWorkItem to resolution_strategy.dart

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

 // Copyright (c) 2017, 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_strategy;
 
 import '../common.dart';
 import '../common_elements.dart';
 import '../common/backend_api.dart';
 import '../common/names.dart';
 import '../common/resolution.dart';
 import '../common/tasks.dart';
+import '../common/work.dart';
 import '../compiler.dart';
 import '../constants/values.dart';
 import '../elements/elements.dart';
 import '../elements/entities.dart';
 import '../elements/modelx.dart';
 import '../elements/resolution_types.dart';
 import '../environment.dart';
 import '../enqueue.dart';
 import '../frontend_strategy.dart';
 import '../js_backend/backend.dart';
@@ skipping 612 matching lines @@
             }
           }
         });
       });
     }
 
     _compiler.libraryLoader.libraries
         .forEach(processJsInteropAnnotationsInLibrary);
   }
 }
+
+/// Builder that creates work item necessary for the resolution of a
+/// [MemberElement].
+class ResolutionWorkItemBuilder extends WorkItemBuilder {
+  final Resolution _resolution;
+
+  ResolutionWorkItemBuilder(this._resolution);
+
+  @override
+  WorkItem createWorkItem(MemberElement element) {
+    assert(invariant(element, element.isDeclaration));
+    if (element.isMalformed) return null;
+
+    assert(invariant(element, element is AnalyzableElement,
+        message: 'Element $element is not analyzable.'));
+    return _resolution.createWorkItem(element);
+  }
+}