telemetry: Make trace profiler work with trace-based benchmarks.

tools/telemetry/telemetry/core/backends/browser_backend.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.
 
 from telemetry.core import util
 from telemetry.core import web_contents
 
 
 class ExtensionsNotSupportedException(Exception):
   pass
@@ skipping 50 matching lines @@
   def supports_system_info(self):
     return False
 
   def StartTracing(self, custom_categories=None,
                    timeout=web_contents.DEFAULT_WEB_CONTENTS_TIMEOUT):
     raise NotImplementedError()
 
   def StopTracing(self):
     raise NotImplementedError()
 
+  def GetTraceResult(self):
+    raise NotImplementedError()
+
   def GetTraceResultAndReset(self):
     raise NotImplementedError()
 
   def GetRemotePort(self, _):
     return util.GetAvailableLocalPort()
 
   def Start(self):
     raise NotImplementedError()
 
   def CreateForwarder(self, *port_pairs):
@@ skipping 15 matching lines @@
   def __init__(self, *port_pairs):
     self._host_port = port_pairs[0].local_port
 
   @property
   def url(self):
     assert self._host_port
     return 'http://127.0.0.1:%i' % self._host_port
 
   def Close(self):
     self._host_port = None