Revert of [telemetry] Script for finding all Telemetry dependencies.

tools/telemetry_tools/path_set.py

-# Copyright (c) 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.
-
-import collections
-import os
-
-
-class PathSet(collections.MutableSet):
-  """A set of paths.
-
-  All mutation methods can take both directories or individual files, but the
-  iterator yields the individual files. All paths are automatically normalized.
-  """
-  def __init__(self, iterable=None):
-    self._paths = set()
-    if iterable:
-      self |= iterable
-
-  def __contains__(self, path):
-    return os.path.realpath(path) in self._paths
-
-  def __iter__(self):
-    return iter(self._paths)
-
-  def __len__(self):
-    return len(self._paths)
-
-  def add(self, path):
-    path = os.path.realpath(path)
-    if os.path.isfile(path):
-      self._paths.add(path)
-    for root, _, files in os.walk(path):
-      for basename in files:
-        file_path = os.path.join(root, basename)
-        if os.path.isfile(file_path):
-          self._paths.add(file_path)
-
-  def discard(self, path):
-    path = os.path.realpath(path)
-    self._paths.discard(path)
-    for root, _, files in os.walk(path):
-      for basename in files:
-        self._paths.discard(os.path.join(root, basename))