Add device port unmapping support to forwarder2.

build/android/pylib/forwarder.py

Index: build/android/pylib/forwarder.py
diff --git a/build/android/pylib/forwarder.py b/build/android/pylib/forwarder.py
index 508d943f7a39df47f575bdfa0bfee705d18f2a56..f5cde9e29da230201fa3c4ec48408c8319f5cb3c 100644
--- a/build/android/pylib/forwarder.py
+++ b/build/android/pylib/forwarder.py
@@ -67,20 +67,20 @@ class Forwarder(object):
     Raises:
       Exception on failure to forward the port.
     """
-    host_adb_control_port = ports.AllocateTestServerPort()
-    if not host_adb_control_port:
+    self._host_adb_control_port = ports.AllocateTestServerPort()
+    if not self._host_adb_control_port:
       raise Exception('Failed to allocate a TCP port in the host machine.')
     self._adb.PushIfNeeded(
         self._device_forwarder_path_on_host, Forwarder._DEVICE_FORWARDER_FOLDER)
     redirection_commands = [
-        '%d:%d:%d:%s' % (host_adb_control_port, device, host,
+        '%d:%d:%d:%s' % (self._host_adb_control_port, device, host,
                          host_name) for device, host in port_pairs]
     logging.info('Command format: <ADB port>:<Device port>' +
                  '[:<Forward to port>:<Forward to address>]')
     logging.info('Forwarding using commands: %s', redirection_commands)
     if cmd_helper.RunCmd(
         ['adb', '-s', self._adb._adb.GetSerialNumber(), 'forward',
-         'tcp:%s' % host_adb_control_port,
+         'tcp:%s' % self._host_adb_control_port,
          'localabstract:%s' % Forwarder._DEVICE_ADB_CONTROL_PORT]) != 0:
       raise Exception('Error while running adb forward.')
 
@@ -114,6 +114,15 @@ class Forwarder(object):
       logging.info('Forwarding device port: %d to host port: %d.', device_port,
                    host_port)
 
+  def UnmapDevicePort(self, device_port):
+    # Please note the minus sign below.
+    redirection_command = '%d:-%d' % (self._host_adb_control_port, device_port)
+    (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
+        [self._host_forwarder_path, redirection_command])
+    if exit_code != 0:
+      raise Exception('%s exited with %d:\n%s' % (
+          self._host_forwarder_path, exit_code, '\n'.join(output)))
+
   @staticmethod
   def KillHost(build_type):
     logging.info('Killing host_forwarder.')