Extract BackendUsage, MirrorsData, and CheckedModeHelpers from Backend.

pkg/compiler/lib/src/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend.namer;
 
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' show JsGetName;
 
 import '../closure.dart';
 import '../common.dart';
 import '../common/names.dart' show Identifiers, Selectors;
 import '../constants/values.dart';
 import '../core_types.dart' show CommonElements;
-import '../elements/resolution_types.dart';
 import '../diagnostics/invariant.dart' show DEBUG_MODE;
 import '../elements/elements.dart';
 import '../elements/entities.dart';
+import '../elements/resolution_types.dart';
+import '../elements/types.dart';
 import '../js/js.dart' as jsAst;
 import '../js/js.dart' show js;
 import '../tree/tree.dart';
 import '../universe/call_structure.dart' show CallStructure;
 import '../universe/selector.dart' show Selector, SelectorKind;
 import '../universe/world_builder.dart' show CodegenWorldBuilder;
 import 'package:front_end/src/fasta/scanner/characters.dart';
 import '../util/util.dart';
 import '../world.dart' show ClosedWorld;
 import 'backend.dart';
@@ skipping 1550 matching lines @@
       new HashMap<ResolutionFunctionType, jsAst.Name>();
   final FunctionTypeNamer functionTypeNamer;
 
   jsAst.Name getFunctionTypeName(ResolutionFunctionType functionType) {
     return functionTypeNameMap.putIfAbsent(functionType, () {
       String proposedName = functionTypeNamer.computeName(functionType);
       return getFreshName(instanceScope, proposedName);
     });
   }
 
-  jsAst.Name operatorIsType(ResolutionDartType type) {
+  jsAst.Name operatorIsType(DartType type) {
     if (type.isFunctionType) {
       // TODO(erikcorry): Reduce from $isx to ix when we are minifying.
       return new CompoundName([
         new StringBackedName(operatorIsPrefix),
         _literalUnderscore,
         getFunctionTypeName(type)
       ]);
     }
-    return operatorIs(type.element);
+    InterfaceType interfaceType = type;
+    return operatorIs(interfaceType.element);
   }
 
   jsAst.Name operatorIs(ClassElement element) {
     // TODO(erikcorry): Reduce from $isx to ix when we are minifying.
     return new CompoundName(
         [new StringBackedName(operatorIsPrefix), runtimeTypeName(element)]);
   }
 
   /// Returns a name that does not clash with reserved JS keywords.
   String _sanitizeForKeywords(String name) {
     if (jsReserved.contains(name)) {
       name = '\$$name';
     }
     assert(!jsReserved.contains(name));
     return name;
   }
 
-  jsAst.Name substitutionName(Element element) {
+  jsAst.Name substitutionName(ClassElement element) {
     return new CompoundName(
         [new StringBackedName(operatorAsPrefix), runtimeTypeName(element)]);
   }
 
   /// Translates a [String] into the corresponding [Name] data structure as
   /// used by the namer.
   ///
   /// If [name] is a setter or getter name, the corresponding [GetterName] or
   /// [SetterName] data structure is used.
   jsAst.Name asName(String name) {
@@ skipping 563 matching lines @@
   void addSuggestion(String original, String suggestion) {
     assert(!_suggestedNames.containsKey(original));
     _suggestedNames[original] = suggestion;
   }
 
   bool hasSuggestion(String original) => _suggestedNames.containsKey(original);
   bool isSuggestion(String candidate) {
     return _suggestedNames.containsValue(candidate);
   }
 }