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

runtime/bin/stdio_patch.dart

Index: runtime/bin/stdio_patch.dart
diff --git a/runtime/bin/stdio_patch.dart b/runtime/bin/stdio_patch.dart
index 482e8d7382245bf531034f77e73b679da0f16388..eb9aa6893baf0c104fd9783a2773d2d665afba88 100644
--- a/runtime/bin/stdio_patch.dart
+++ b/runtime/bin/stdio_patch.dart
@@ -12,7 +12,7 @@ patch class _StdIOUtils {
       case _STDIO_HANDLE_TYPE_FILE:
         return new Stdin._(new _FileStream.forStdin());
       default:
-        throw new FileException("Unsupported stdin type");
+        throw new FileSystemException("Unsupported stdin type");
     }
   }
 
@@ -26,14 +26,14 @@ patch class _StdIOUtils {
       case _STDIO_HANDLE_TYPE_FILE:
         return new _StdSink(new IOSink(new _FileStreamConsumer.fromStdio(fd)));
       default:
-        throw new FileException("Unsupported stdin type");
+        throw new FileSystemException("Unsupported stdin type");
     }
   }
 
   static int _socketType(nativeSocket) {
     var result = _getSocketType(nativeSocket);
     if (result is OSError) {
-      throw new FileException("Error retreiving socket type", result);
+      throw new FileSystemException("Error retreiving socket type", result);
     }
     return result;
   }