Remove the task tracking stuff in the bindings.

mojo/environment/BUILD.gn

 # Copyright 2014 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.
 
 source_set("chromium") {
   sources = [
     "default_async_waiter.cc",
     "default_async_waiter.h",
     "default_logger.cc",
     "default_logger.h",
-    "default_task_tracker.cc",
-    "default_task_tracker.h",
     "environment.cc",
 
     # TODO(vtl): This is kind of ugly. (See TODO in logging.h.)
     "../public/cpp/environment/async_waiter.h",
     "../public/cpp/environment/lib/async_waiter.cc",
     "../public/cpp/environment/lib/logging.cc",
-    "../public/cpp/environment/lib/scoped_task_tracking.cc",
-    "../public/cpp/environment/lib/scoped_task_tracking.h",
     "../public/cpp/environment/logging.h",
   ]
 
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
     "//mojo/common",
     "//mojo/message_pump",
     "//mojo/public/c/environment",
     "//mojo/public/cpp/bindings:callback",
     "//mojo/public/cpp/environment",
     "//mojo/public/cpp/system",
   ]
 }