Change js_emitter parts into libraries

pkg/compiler/lib/src/js_emitter/metadata_collector.dart

 // Copyright (c) 2013, 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.
 
-part of dart2js.js_emitter;
+library dart2js.js_emitter.metadata_collector;
+
+import 'package:js_ast/src/precedence.dart' as js_precedence;
+
+import '../common.dart';
+import '../compiler.dart' show Compiler;
+import '../constants/values.dart';
+import '../elements/resolution_types.dart'
+    show
+    ResolutionDartType,
+    ResolutionTypedefType;
+import '../deferred_load.dart' show OutputUnit;
+import '../elements/elements.dart'
+    show
+    ConstructorElement,
+    Element,
+    FunctionElement,
+    FunctionSignature,
+    MetadataAnnotation,
+    ParameterElement;
+import '../js/js.dart' as jsAst;
+import '../js/js.dart' show js;
+import '../js_backend/js_backend.dart'
+    show
+    JavaScriptBackend,
+    TypeVariableHandler;
+
+import 'code_emitter_task.dart' show Emitter;
 
 /// Represents an entry's position in one of the global metadata arrays.
 ///
 /// [_rc] is used to count the number of references of the token in the
 /// ast for a program.
 /// [value] is the actual position, once they have been finalized.
 abstract class _MetadataEntry extends jsAst.DeferredNumber
     implements Comparable, jsAst.ReferenceCountedAstNode {
   jsAst.Expression get entry;
   int get value;
@@ skipping 408 matching lines @@
     if (token is _ForwardingMetadataEntry && !token.isBound) {
       _foundUnboundToken = true;
     }
   }
 
   bool findUnboundPlaceholders(jsAst.Node node) {
     node.accept(this);
     return _foundUnboundToken;
   }
 }