webrtc: Fix missing port forwarding on CrOS

telemetry/telemetry/core/platform.py

 # Copyright 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 logging as real_logging
 import os
 import sys
 
 from telemetry.core import local_server
 from telemetry.core import memory_cache_http_server
 from telemetry.core import network_controller
 from telemetry.core import tracing_controller
 from telemetry.core import util
+from telemetry.internal import forwarders
 from telemetry.internal.platform import (platform_backend as
                                          platform_backend_module)
 
 from py_utils import discover
 
 _host_platform = None
 # Remote platform is a dictionary from device ids to remote platform instances.
 _remote_platforms = {}
 
 
@@ skipping 58 matching lines @@
     self._platform_backend = platform_backend
     self._platform_backend.InitPlatformBackend()
     self._platform_backend.SetPlatform(self)
     self._network_controller = network_controller.NetworkController(
         self._platform_backend.network_controller_backend)
     self._tracing_controller = tracing_controller.TracingController(
         self._platform_backend.tracing_controller_backend)
     self._local_server_controller = local_server.LocalServerController(
         self._platform_backend)
     self._is_monitoring_power = False
+    self._forwarder = None
 
   @property
   def is_host_platform(self):
     return self == GetHostPlatform()
 
   @property
   def network_controller(self):
     """Control network settings and servers to simulate the Web."""
     return self._network_controller
 
@@ skipping 302 matching lines @@
       if paths and self.http_server.paths == paths:
         return False
 
       self.http_server.Close()
 
     if not paths:
       return False
 
     server = memory_cache_http_server.MemoryCacheHTTPServer(paths)
     self.StartLocalServer(server)
+
+    # Requires port forwarding if browser is on remote device, and
+    # replaces the http_server port number with the one resolved by
+    # remote machine with ssh/adb remote port forwarding.
+    if self._platform_backend.IsDeviceRemote():
+      # TODO(crbug.com/747293):
+      # Originally the proxy_server is enabled for forwarding traffic
+      # if the device is on remote. However, if the tracing is enabled,
+      # the browser startup args will be reset which disables traffic
+      # reroute through proxy_server. Here we have to create extra
+      # port_forwarding.
+      if self.tracing_controller.is_tracing_running:
+        self._forwarder = self._platform_backend.CreatePortForwarder(
+            forwarders.PortPair(self.http_server.port, 0),
+            use_remote_port_forwarding=True)
+        self.http_server.port = self._forwarder.host_port
     return True
 
   def StopAllLocalServers(self):
     self._local_server_controller.Close()
+    if self._forwarder:
+      self._forwarder.Close()
 
   @property
   def local_servers(self):
     """Returns the currently running local servers."""
     return self._local_server_controller.local_servers
 
   def HasBattOrConnected(self):
     return  self._platform_backend.HasBattOrConnected()
 
   def WaitForBatteryTemperature(self, temp):
     """Waits for the battery on the device under test to cool down to temp.
 
     Args:
       temp: temperature target in degrees C.
     """
     return self._platform_backend.WaitForBatteryTemperature(temp)