Clean up package imports and library names

pkg/analyzer/lib/file_system/physical_file_system.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 physical_file_system;
+library analyzer.file_system.physical_file_system;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 import 'dart:io' as io;
 
+import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/util/absolute_path.dart';
 import 'package:path/path.dart';
 import 'package:watcher/watcher.dart';
 
-import 'file_system.dart';
-
 /**
  * A `dart:io` based implementation of [ResourceProvider].
  */
 class PhysicalResourceProvider implements ResourceProvider {
   static final NORMALIZE_EOL_ALWAYS = (String string) =>
       string.replaceAll(new RegExp('\r\n?'), '\n');
 
   static final PhysicalResourceProvider INSTANCE =
       new PhysicalResourceProvider(null);
 
@@ skipping 191 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }