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

pkg/compiler/lib/src/native/native.dart

 // Copyright (c) 2012, 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 native;
 
-import 'dart:collection' show Queue;
+import '../compiler.dart' show Compiler;
+import '../elements/elements.dart';
 
-import '../common.dart';
-import '../common/backend_api.dart' show
-    ForeignResolver;
-import '../common/registry.dart' show
-    Registry;
-import '../common/resolution.dart' show
-    Parsing,
-    Resolution;
-import '../compiler.dart' show
-    Compiler;
-import '../constants/values.dart';
-import '../core_types.dart' show
-    CoreTypes;
-import '../dart_types.dart';
-import '../enqueue.dart' show
-    Enqueuer,
-    ResolutionEnqueuer;
-import '../elements/elements.dart';
-import '../elements/modelx.dart' show
-    BaseClassElementX,
-    ElementX,
-    FunctionElementX,
-    LibraryElementX;
-import '../js/js.dart' as js;
-import '../js_backend/backend_helpers.dart' show
-    BackendHelpers;
-import '../js_backend/js_backend.dart';
-import '../js_emitter/js_emitter.dart' show
-    CodeEmitterTask,
-    NativeEmitter;
-import '../parser/listener.dart' show
-    Listener;
-import '../parser/element_listener.dart' show
-    ElementListener;
-import '../ssa/ssa.dart';
-import '../tokens/token.dart' show
-    BeginGroupToken,
-    Token;
-import '../tokens/token_constants.dart' as Tokens show
-    EOF_TOKEN,
-    STRING_TOKEN;
-import '../tree/tree.dart';
-import '../universe/side_effects.dart' show
-    SideEffects;
-import '../util/util.dart';
-
-part 'behavior.dart';
-part 'enqueue.dart';
-part 'js.dart';
-part 'scanner.dart';
-part 'ssa.dart';
+export 'behavior.dart';
+export 'enqueue.dart';
+export 'js.dart';
+export 'scanner.dart';
+export 'ssa.dart';
 
 bool maybeEnableNative(Compiler compiler,
                        LibraryElement library) {
   String libraryName = library.canonicalUri.toString();
   if (library.entryCompilationUnit.script.name.contains(
           'sdk/tests/compiler/dart2js_native')
       || library.entryCompilationUnit.script.name.contains(
           'sdk/tests/compiler/dart2js_extra')
       || libraryName == 'dart:async'
       || libraryName == 'dart:html'
       || libraryName == 'dart:html_common'
       || libraryName == 'dart:indexed_db'
       || libraryName == 'dart:js'
       || libraryName == 'dart:svg'
       || libraryName == 'dart:_native_typed_data'
       || libraryName == 'dart:web_audio'
       || libraryName == 'dart:web_gl'
       || libraryName == 'dart:web_sql'
       || compiler.allowNativeExtensions) {
     return true;
   }
   return false;
 }