[telemetry] Timeline model cleanups

tools/telemetry/telemetry/core/timeline/tracing/slice.py

-# Copyright 2013 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 telemetry.core.timeline.event as timeline_event
-
-class Slice(timeline_event.TimelineEvent):
-  ''' A Slice represents an interval of time plus parameters associated
-  with that interval.
-
-  NOTE: The Sample class implements the same interface as
-  Slice. These must be kept in sync.
-
-  All time units are stored in milliseconds.
-  '''
-  def __init__(self, category, name, timestamp, args=None, parent=None):
-    super(Slice, self).__init__(
-        name, timestamp, 0, args=args, parent=parent)
-    self._sub_slices = []
-    self.category = category
-    self.did_not_finish = False
-
-  @property
-  def sub_slices(self):
-    return self._sub_slices
-
-  def AddSubSlice(self, sub_slice):
-    self._sub_slices.append(sub_slice)
-
-  def _GetSubSlicesRecursive(self):
-    for sub_slice in self._sub_slices:
-      for s in sub_slice.GetAllSubSlices():
-        yield s
-      yield sub_slice
-
-  def GetAllSubSlices(self):
-    return list(self._GetSubSlicesRecursive())
-
-  def GetAllSubSlicesOfName(self, name):
-    return [e for e in self.GetAllSubSlices() if e.name == name]