Move InheritanceManager to its own file.

pkg/analyzer/test/generated/inheritance_manager_test.dart

 // Copyright (c) 2016, 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.test.generated.inheritance_manager_test;
 
 import 'dart:collection';
 
 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/resolver/inheritance_manager.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/java_engine_io.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/generated/testing/ast_factory.dart';
 import 'package:analyzer/src/generated/testing/element_factory.dart';
 import 'package:analyzer/src/generated/testing/test_type_provider.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 1238 matching lines @@
         new FileBasedSource(FileUtilities2.createFile("/test.dart"));
     CompilationUnitElementImpl definingCompilationUnit =
         new CompilationUnitElementImpl("test.dart");
     definingCompilationUnit.librarySource =
         definingCompilationUnit.source = source;
     _definingLibrary = ElementFactory.library(context, "test");
     _definingLibrary.definingCompilationUnit = definingCompilationUnit;
     return new InheritanceManager(_definingLibrary);
   }
 }