sandwich: Refactor to use more existing code.

tools/android/loading/tracing.py

 # Copyright 2016 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.
 
 """Monitor tracing events on chrome via chrome remote debugging."""
 
 import bisect
 import itertools
 import logging
 import operator
 
 import devtools_monitor
 
 
+DEFAULT_CATEGORIES = None
+
+
 class TracingTrack(devtools_monitor.Track):
   """Grabs and processes trace event messages.
 
   See https://goo.gl/Qabkqk for details on the protocol.
   """
-  def __init__(self, connection, categories=None, fetch_stream=False):
+  def __init__(self, connection,
+               categories=DEFAULT_CATEGORIES,
+               fetch_stream=False):
     """Initialize this TracingTrack.
 
     Args:
       connection: a DevToolsConnection.
       categories: None, or a string, or list of strings, of tracing categories
         to filter.
 
       fetch_stream: if true, use a websocket stream to fetch tracing data rather
         than dataCollected events. It appears based on very limited testing that
         a stream is slower than the default reporting as dataCollected events.
@@ skipping 266 matching lines @@
                   if 'dur' in tracing_event else tracing_event['tdur'])
       self.end_msec = self.start_msec + duration / 1000.0
 
   @property
   def type(self):
     if self._synthetic:
       return None
     return self._tracing_event['ph']
 
   @property
+  def category(self):
+    return self._tracing_event['cat']
+
+  @property
+  def pid(self):
+    return self._tracing_event['pid']
+
+  @property
   def args(self):
     return self._tracing_event.get('args', {})
 
   @property
   def id(self):
     return self._tracing_event.get('id')
 
   @property
   def name(self):
     return self._tracing_event['name']
@@ skipping 138 matching lines @@
     self._left = _IntervalTree(self.start, left_end, left_events)
     self._right = _IntervalTree(right_start, self.end, right_events)
 
   def _IsLeaf(self):
     return self._left is None
 
   @classmethod
   def _Overlaps(cls, event, start, end):
     return (min(end, event.end_msec) - max(start, event.start_msec) > 0
             or start <= event.start_msec < end)  # For instant events.