Merge "FileImage: make thread-safe"

    self.clobbered_blocks = RangeSet()

    self.extended = RangeSet()

    self.generator_lock = threading.Lock()

    self.hashtree_info = None

    if hashtree_info_generator:

      self.hashtree_info = hashtree_info_generator.Generate(self)

    self._file.close()

  def _GetRangeData(self, ranges):

    # Use a lock to protect the generator so that we will not run two

    # instances of this generator on the same object simultaneously.

    with self.generator_lock:

      for s, e in ranges:

        self._file.seek(s * self.blocksize)

        for _ in range(s, e):