Use Dart 2 constants (dart-lang/watcher#60)

diff --git a/pkgs/watcher/CHANGELOG.md b/pkgs/watcher/CHANGELOG.md
index fe30bc6..d8f2d5f 100644
--- a/pkgs/watcher/CHANGELOG.md
+++ b/pkgs/watcher/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 0.9.7+9
+
+* Internal changes only.
+
 # 0.9.7+8
 
 * Fix Dart 2.0 type issues on Mac and Windows.
diff --git a/pkgs/watcher/lib/src/constructable_file_system_event.dart b/pkgs/watcher/lib/src/constructable_file_system_event.dart
index a0f153e..29b7c8d 100644
--- a/pkgs/watcher/lib/src/constructable_file_system_event.dart
+++ b/pkgs/watcher/lib/src/constructable_file_system_event.dart
@@ -14,7 +14,7 @@
 
 class ConstructableFileSystemCreateEvent extends _ConstructableFileSystemEvent
     implements FileSystemCreateEvent {
-  final type = FileSystemEvent.CREATE;
+  final type = FileSystemEvent.create;
 
   ConstructableFileSystemCreateEvent(String path, bool isDirectory)
       : super(path, isDirectory);
@@ -24,7 +24,7 @@
 
 class ConstructableFileSystemDeleteEvent extends _ConstructableFileSystemEvent
     implements FileSystemDeleteEvent {
-  final type = FileSystemEvent.DELETE;
+  final type = FileSystemEvent.delete;
 
   ConstructableFileSystemDeleteEvent(String path, bool isDirectory)
       : super(path, isDirectory);
@@ -35,7 +35,7 @@
 class ConstructableFileSystemModifyEvent extends _ConstructableFileSystemEvent
     implements FileSystemModifyEvent {
   final bool contentChanged;
-  final type = FileSystemEvent.MODIFY;
+  final type = FileSystemEvent.modify;
 
   ConstructableFileSystemModifyEvent(
       String path, bool isDirectory, this.contentChanged)
@@ -48,7 +48,7 @@
 class ConstructableFileSystemMoveEvent extends _ConstructableFileSystemEvent
     implements FileSystemMoveEvent {
   final String destination;
-  final type = FileSystemEvent.MOVE;
+  final type = FileSystemEvent.move;
 
   ConstructableFileSystemMoveEvent(
       String path, bool isDirectory, this.destination)
diff --git a/pkgs/watcher/lib/src/directory_watcher/mac_os.dart b/pkgs/watcher/lib/src/directory_watcher/mac_os.dart
index 5ad9984..9da413a 100644
--- a/pkgs/watcher/lib/src/directory_watcher/mac_os.dart
+++ b/pkgs/watcher/lib/src/directory_watcher/mac_os.dart
@@ -244,13 +244,13 @@
 
       // If we previously thought this was a MODIFY, we now consider it to be a
       // CREATE or REMOVE event. This is safe for the same reason as above.
-      if (type == FileSystemEvent.MODIFY) {
+      if (type == FileSystemEvent.modify) {
         type = event.type;
         continue;
       }
 
       // A CREATE event contradicts a REMOVE event and vice versa.
-      assert(type == FileSystemEvent.CREATE || type == FileSystemEvent.DELETE);
+      assert(type == FileSystemEvent.create || type == FileSystemEvent.delete);
       if (type != event.type) return null;
     }
 
@@ -258,23 +258,23 @@
     // from FSEvents reporting an add that happened prior to the watch
     // beginning. If we also received a MODIFY event, we want to report that,
     // but not the CREATE.
-    if (type == FileSystemEvent.CREATE &&
+    if (type == FileSystemEvent.create &&
         hadModifyEvent &&
         _files.contains(batch.first.path)) {
-      type = FileSystemEvent.MODIFY;
+      type = FileSystemEvent.modify;
     }
 
     switch (type) {
-      case FileSystemEvent.CREATE:
+      case FileSystemEvent.create:
         // Issue 16003 means that a CREATE event for a directory can indicate
         // that the directory was moved and then re-created.
         // [_eventsBasedOnFileSystem] will handle this correctly by producing a
         // DELETE event followed by a CREATE event if the directory exists.
         if (isDir) return null;
         return new ConstructableFileSystemCreateEvent(batch.first.path, false);
-      case FileSystemEvent.DELETE:
+      case FileSystemEvent.delete:
         return new ConstructableFileSystemDeleteEvent(batch.first.path, isDir);
-      case FileSystemEvent.MODIFY:
+      case FileSystemEvent.modify:
         return new ConstructableFileSystemModifyEvent(
             batch.first.path, isDir, false);
       default:
diff --git a/pkgs/watcher/lib/src/directory_watcher/windows.dart b/pkgs/watcher/lib/src/directory_watcher/windows.dart
index db9ca83..0e550ae 100644
--- a/pkgs/watcher/lib/src/directory_watcher/windows.dart
+++ b/pkgs/watcher/lib/src/directory_watcher/windows.dart
@@ -132,7 +132,7 @@
       // the directory is now gone.
       if (event is FileSystemMoveEvent ||
           event is FileSystemDeleteEvent ||
-          (FileSystemEntity.typeSync(path) == FileSystemEntityType.NOT_FOUND)) {
+          (FileSystemEntity.typeSync(path) == FileSystemEntityType.notFound)) {
         for (var path in _files.paths) {
           _emitEvent(ChangeType.REMOVE, path);
         }
@@ -283,27 +283,27 @@
 
       // If we previously thought this was a MODIFY, we now consider it to be a
       // CREATE or REMOVE event. This is safe for the same reason as above.
-      if (type == FileSystemEvent.MODIFY) {
+      if (type == FileSystemEvent.modify) {
         type = event.type;
         continue;
       }
 
       // A CREATE event contradicts a REMOVE event and vice versa.
-      assert(type == FileSystemEvent.CREATE ||
-          type == FileSystemEvent.DELETE ||
-          type == FileSystemEvent.MOVE);
+      assert(type == FileSystemEvent.create ||
+          type == FileSystemEvent.delete ||
+          type == FileSystemEvent.move);
       if (type != event.type) return null;
     }
 
     switch (type) {
-      case FileSystemEvent.CREATE:
+      case FileSystemEvent.create:
         return new ConstructableFileSystemCreateEvent(batch.first.path, isDir);
-      case FileSystemEvent.DELETE:
+      case FileSystemEvent.delete:
         return new ConstructableFileSystemDeleteEvent(batch.first.path, isDir);
-      case FileSystemEvent.MODIFY:
+      case FileSystemEvent.modify:
         return new ConstructableFileSystemModifyEvent(
             batch.first.path, isDir, false);
-      case FileSystemEvent.MOVE:
+      case FileSystemEvent.move:
         return null;
       default:
         throw 'unreachable';
diff --git a/pkgs/watcher/lib/src/file_watcher/native.dart b/pkgs/watcher/lib/src/file_watcher/native.dart
index 8e7dd09..5f56f73 100644
--- a/pkgs/watcher/lib/src/file_watcher/native.dart
+++ b/pkgs/watcher/lib/src/file_watcher/native.dart
@@ -49,7 +49,7 @@
   }
 
   void _onBatch(List<FileSystemEvent> batch) {
-    if (batch.any((event) => event.type == FileSystemEvent.DELETE)) {
+    if (batch.any((event) => event.type == FileSystemEvent.delete)) {
       // If the file is deleted, the underlying stream will close. We handle
       // emitting our own REMOVE event in [_onDone].
       return;
diff --git a/pkgs/watcher/pubspec.yaml b/pkgs/watcher/pubspec.yaml
index 3cb9643..2f449ff 100644
--- a/pkgs/watcher/pubspec.yaml
+++ b/pkgs/watcher/pubspec.yaml
@@ -1,12 +1,12 @@
 name: watcher
-version: 0.9.7+8
+version: 0.9.7+9
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/watcher
 description: >
   A file system watcher. It monitors changes to contents of directories and
   sends notifications when files have been added, removed, or modified.
 environment:
-  sdk: '>=2.0.0-dev.20.0 <2.0.0'
+  sdk: '>=2.0.0-dev.61.0 <2.0.0'
 dependencies:
   async: '>=1.10.0 <3.0.0'
   path: '>=0.9.0 <2.0.0'