Reland [telemetry] Timeline model cleanups

tools/telemetry/telemetry/core/chrome/tracing_backend.py

 # Copyright (c) 2012 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 cStringIO
 import json
 import logging
 import socket
 import threading
 
@@ skipping 25 matching lines @@
     else:
       f.write(d[0])
       for i in range(1, len(d)):
         f.write(',')
         f.write(d[i])
     f.write(']}')
 
   def AsTimelineModel(self):
     f = cStringIO.StringIO()
     self.Serialize(f)
-    return model.TimelineModel(event_data=f.getvalue())
+    return model.TimelineModel(
+      event_data=f.getvalue(),
+      shift_world_to_zero=False)
 
 class TracingBackend(object):
   def __init__(self, devtools_port):
     debugger_url = 'ws://localhost:%i/devtools/browser' % devtools_port
     self._socket = websocket.create_connection(debugger_url)
     self._next_request_id = 0
     self._cur_socket_timeout = 0
     self._thread = None
     self._tracing_data = []
 
@@ skipping 68 matching lines @@
       logging.debug('got [%s]', data)
       res = json.loads(data)
       if res['id'] != req['id']:
         logging.debug('Dropped reply: %s', json.dumps(res))
         continue
       if res.get('response'):
         raise TracingUnsupportedException(
             'Tracing not supported for this browser')
       elif 'error' in res:
         return