Remove the task tracking stuff in the bindings.

mojo/environment/default_task_tracker.h

Index: mojo/environment/default_task_tracker.h
diff --git a/mojo/environment/default_task_tracker.h b/mojo/environment/default_task_tracker.h
deleted file mode 100644
index f1f43e50e2430fa2f8d992d639c8457779d2d195..0000000000000000000000000000000000000000
--- a/mojo/environment/default_task_tracker.h
+++ /dev/null
@@ -1,19 +0,0 @@
-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef MOJO_ENVIRONMENT_DEFAULT_TASK_TRACKER_H_
-#define MOJO_ENVIRONMENT_DEFAULT_TASK_TRACKER_H_
-
-namespace mojo {
-
-struct TaskTracker;
-
-namespace internal {
-
-extern const TaskTracker kDefaultTaskTracker;
-
-}  // namespace internal
-}  // namespace mojo
-
-#endif  // MOJO_ENVIRONMENT_DEFAULT_TASK_TRACKER_H_