Remove DirectoryException and LinkException from dart:io and use FileException instaed.

runtime/bin/file_patch.dart

Index: runtime/bin/file_patch.dart
diff --git a/runtime/bin/file_patch.dart b/runtime/bin/file_patch.dart
index 1fb9b90d943a714b0ccd5d0010b6c4b4627ed565..907b7f2aeda9476ee8b188e04dfe2b3cbdd9917d 100644
--- a/runtime/bin/file_patch.dart
+++ b/runtime/bin/file_patch.dart
@@ -57,7 +57,7 @@ class _FileSystemWatcherImpl
 
   _FileSystemWatcherImpl(this._path, this._events, this._recursive) {
     if (!isSupported) {
-      throw new FileException(
+      throw new FileSystemException(
           "File system watching is not supported on this system",
           _path);
     }
@@ -69,7 +69,7 @@ class _FileSystemWatcherImpl
     try {
       socketId = _watchPath(_path, _events, identical(true, _recursive));
     } catch (e) {
-      throw new FileException(
+      throw new FileSystemException(
           "Failed to watch path",
           _path,
           e);