Make startup of of WPR components resilient to not starting up previous steps.

This fixes the redness in the orderfile bot due to the WPR server failing to
start due to certs not being installed.

Review URL: https://codereview.chromium.org/1089163004

Cr-Commit-Position: refs/heads/master@{#325229}

tools/cygprofile/profile_android_startup.py

@@ -135,12 +135,14 @@ class WprManager(object):
     """Start the WPR server on the host and the forwarder on the device."""
     print 'Starting WPR on host...'
     _DownloadFromCloudStorage(self._WPR_BUCKET, self._wpr_archive_hash)
-    self._wpr_server = webpagereplay.ReplayServer(self._wpr_archive,
-        '127.0.0.1', 0, 0, None,
-        ['--should_generate_certs',
-         '--https_root_ca_cert_path=' + self._wpr_ca_cert_path,
-         '--use_closest_match'])
-    ports = self._wpr_server.StartServer()[:-1]
+    args = ['--user_closest_match']
+    if self._is_test_ca_installed:
+      args.extend(['--should_generate_certs',
+                   '--https_root_ca_cert_path=' + self._wpr_ca_cert_path])
+    wpr_server = webpagereplay.ReplayServer(self._wpr_archive,
+        '127.0.0.1', 0, 0, None, args)
+    ports = wpr_server.StartServer()[:-1]
+    self._wpr_server = wpr_server
     self._host_http_port = ports[0]
     self._host_https_port = ports[1]
 
@@ -149,11 +151,15 @@ class WprManager(object):
     print 'Stopping WPR on host...'
     if self._wpr_server:
       self._wpr_server.StopServer()
+      self._wpr_server = None
 
   def _StartForwarder(self):
     """Sets up forwarding of device ports to the host, and configures chrome
     to use those ports.
     """
+    if not self._wpr_server:
+      logging.warning('No host WPR server to forward to.')
+      return
     print 'Starting device forwarder...'
     forwarder.Forwarder.Map([(0, self._host_http_port),
                              (0, self._host_https_port)],