Revert 107895 - Fully enable about:tracking by default

base/tracking_info.cc

-// Copyright (c) 2011 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.
-
-#include "base/tracking_info.h"
-
-#include "base/tracked_objects.h"
-
-namespace base {
-
-TrackingInfo::TrackingInfo(
-    const tracked_objects::Location& posted_from,
-    base::TimeTicks delayed_run_time)
-    : birth_tally(
-          tracked_objects::ThreadData::TallyABirthIfActive(posted_from)),
-      time_posted(TimeTicks::Now()),
-      delayed_run_time(delayed_run_time) {
-}
-
-TrackingInfo::~TrackingInfo() {}
-
-}  // namespace base
-