Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/watcher/lib/src/file_watcher.dart

Index: mojo/public/dart/third_party/watcher/lib/src/file_watcher.dart
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+// Copyright (c) 2015, 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 watcher.file_watcher;
+
+import 'dart:io';
+
+import 'watch_event.dart';
+import '../watcher.dart';
+import 'file_watcher/native.dart';
+import 'file_watcher/polling.dart';
+
+/// Watches a file and emits [WatchEvent]s when the file has changed.
+///
+/// Note that since each watcher only watches a single file, it will only emit
+/// [ChangeType.MODIFY] events, except when the file is deleted at which point
+/// it will emit a single [ChangeType.REMOVE] event and then close the stream.
+///
+/// If the file is deleted and quickly replaced (when a new file is moved in its
+/// place, for example) this will emit a [ChangeTime.MODIFY] event.
+abstract class FileWatcher implements Watcher {
+  /// Creates a new [FileWatcher] monitoring [file].
+  ///
+  /// If a native file watcher is available for this platform, this will use it.
+  /// Otherwise, it will fall back to a [PollingFileWatcher]. Notably, native
+  /// file watching is *not* supported on Windows.
+  ///
+  /// If [pollingDelay] is passed, it specifies the amount of time the watcher
+  /// will pause between successive polls of the directory contents. Making this
+  /// shorter will give more immediate feedback at the expense of doing more IO
+  /// and higher CPU usage. Defaults to one second. Ignored for non-polling
+  /// watchers.
+  factory FileWatcher(String file, {Duration pollingDelay}) {
+    // [File.watch] doesn't work on Windows, but
+    // [FileSystemEntity.isWatchSupported] is still true because directory
+    // watching does work.
+    if (FileSystemEntity.isWatchSupported && !Platform.isWindows) {
+      return new NativeFileWatcher(file);
+    }
+    return new PollingFileWatcher(file, pollingDelay: pollingDelay);
+  }
+}