Move InheritanceManager to its own file.

pkg/analyzer/lib/src/task/strong_mode.dart

 // Copyright (c) 2015, 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 analyzer.src.task.strong_mode;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/generated/resolver.dart'
     show TypeProvider, InheritanceManager;
 import 'package:analyzer/src/generated/type_system.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
+import 'package:analyzer/src/dart/resolver/inheritance_manager.dart';
 
 /**
  * Sets the type of the field. This is stored in the field itself, and the
  * synthetic getter/setter types.
  */
 void setFieldType(VariableElement field, DartType newType) {
   (field as VariableElementImpl).type = newType;
   if (field.initializer != null) {
     (field.initializer as ExecutableElementImpl).returnType = newType;
   }
@@ skipping 447 matching lines @@
         results.add(element);
       }
     }
   }
 }
 
 /**
  * A class of exception that is not used anywhere else.
  */
 class _CycleException implements Exception {}