Cleanup 1: split parts into their own libraries, remove unused imports

pkg/compiler/lib/src/js_backend/codegen/glue.dart

 // Copyright (c) 2014, 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 code_generator_dependencies;
 
 import '../backend_helpers.dart' show
     BackendHelpers;
 import '../js_backend.dart';
 
 import '../../common.dart';
-import '../../common/registry.dart' show
-    Registry;
 import '../../common/codegen.dart' show
     CodegenRegistry;
 import '../../compiler.dart' show
     Compiler;
 import '../../constants/values.dart';
 import '../../dart_types.dart' show
     DartType,
     TypeVariableType,
     InterfaceType;
 import '../../enqueue.dart' show
@@ skipping 269 matching lines @@
   FunctionElement get closureFromTearOff => _backend.helpers.closureFromTearOff;
 
   js.Name registerOneShotInterceptor(Selector selector) {
     return _backend.registerOneShotInterceptor(selector);
   }
 
   bool mayGenerateInstanceofCheck(DartType type) {
     return _backend.mayGenerateInstanceofCheck(type);
   }
 }