[WIP] DevToolsClientBackend with tracing API.

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

Index: tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py b/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
deleted file mode 100644
index 62426419bdc07504e10264d4b74b915761da93a8..0000000000000000000000000000000000000000
--- a/tools/telemetry/telemetry/core/backends/chrome/tracing_backend.py
+++ /dev/null
@@ -1,130 +0,0 @@
-# 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 logging
-
-from telemetry.core.backends.chrome_inspector import inspector_websocket
-from telemetry.core.platform import tracing_options
-
-
-class TracingUnsupportedException(Exception):
-  pass
-
-
-class TracingTimeoutException(Exception):
-  pass
-
-class TracingHasNotRunException(Exception):
-  pass
-
-
-class TracingBackend(object):
-  def __init__(self, devtools_port, chrome_browser_backend):
-    self._inspector_websocket = inspector_websocket.InspectorWebsocket(
-        self._ErrorHandler)
-    self._inspector_websocket.RegisterDomain(
-        'Tracing', self._NotificationHandler)
-
-    self._inspector_websocket.Connect(
-        'ws://127.0.0.1:%i/devtools/browser' % devtools_port)
-    self._tracing_data = []
-    self._is_tracing_running = False
-    self._chrome_browser_backend = chrome_browser_backend
-
-  @property
-  def is_tracing_running(self):
-    return self._is_tracing_running
-
-  @property
-  def _devtools_client(self):
-    return self._chrome_browser_backend.devtools_client
-
-  def StartTracing(self, trace_options, custom_categories=None, timeout=10):
-    """ Starts tracing on the first call and returns True. Returns False
-        and does nothing on subsequent nested calls.
-    """
-    if self.is_tracing_running:
-      return False
-    # Reset collected tracing data from previous tracing calls.
-    self._tracing_data = []
-    self._CheckNotificationSupported()
-    #TODO(nednguyen): remove this when the stable branch pass 2118.
-    if (trace_options.record_mode == tracing_options.RECORD_AS_MUCH_AS_POSSIBLE
-        and self._devtools_client.GetChromeBranchNumber()
-        and self._devtools_client.GetChromeBranchNumber() < 2118):
-      logging.warning(
-          'Cannot use %s tracing mode on chrome browser with branch version %i,'
-          ' (<2118) fallback to use %s tracing mode' % (
-              trace_options.record_mode,
-              self._devtools_client.GetChromeBranchNumber(),
-              tracing_options.RECORD_UNTIL_FULL))
-      trace_options.record_mode = tracing_options.RECORD_UNTIL_FULL
-    req = {'method': 'Tracing.start'}
-    req['params'] = {}
-    m = {tracing_options.RECORD_UNTIL_FULL: 'record-until-full',
-         tracing_options.RECORD_AS_MUCH_AS_POSSIBLE:
-         'record-as-much-as-possible'}
-    req['params']['options'] = m[trace_options.record_mode]
-    if custom_categories:
-      req['params']['categories'] = custom_categories
-    self._inspector_websocket.SyncRequest(req, timeout)
-    self._is_tracing_running = True
-    return True
-
-  def StopTracing(self, timeout=30):
-    """ Stops tracing and returns the raw json trace result. It this is called
-    after tracing has been stopped, trace data from the last tracing run is
-    returned.
-    """
-    if not self.is_tracing_running:
-      if not self._tracing_data:
-        raise TracingHasNotRunException()
-      else:
-        return self._tracing_data
-    req = {'method': 'Tracing.end'}
-    self._inspector_websocket.SendAndIgnoreResponse(req)
-    # After Tracing.end, chrome browser will send asynchronous notifications
-    # containing trace data. This is until Tracing.tracingComplete is sent,
-    # which means there is no trace buffers pending flush.
-    try:
-      self._inspector_websocket.DispatchNotificationsUntilDone(timeout)
-    except \
-        inspector_websocket.DispatchNotificationsUntilDoneTimeoutException \
-        as err:
-      raise TracingTimeoutException(
-          'Trace data was not fully received due to timeout after %s '
-          'seconds. If the trace data is big, you may want to increase the '
-          'time out amount.' % err.elapsed_time)
-    self._is_tracing_running = False
-    return self._tracing_data
-
-  def _ErrorHandler(self, elapsed):
-    logging.error('Unrecoverable error after %ds reading tracing response.',
-                  elapsed)
-    raise
-
-  def _NotificationHandler(self, res):
-    if 'Tracing.dataCollected' == res.get('method'):
-      value = res.get('params', {}).get('value')
-      if type(value) in [str, unicode]:
-        self._tracing_data.append(value)
-      elif type(value) is list:
-        self._tracing_data.extend(value)
-      else:
-        logging.warning('Unexpected type in tracing data')
-    elif 'Tracing.tracingComplete' == res.get('method'):
-      return True
-
-  def Close(self):
-    self._inspector_websocket.Disconnect()
-
-  def _CheckNotificationSupported(self):
-    """Ensures we're running against a compatible version of chrome."""
-    req = {'method': 'Tracing.hasCompleted'}
-    res = self._inspector_websocket.SyncRequest(req)
-    if res.get('response'):
-      raise TracingUnsupportedException(
-          'Tracing not supported for this browser')
-    elif 'error' in res:
-      return