Ensure manifest exists in Port._wpt_manifest.

third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_cl_unittest.py

 # Copyright 2016 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 json
 import optparse
 
 from webkitpy.common.net.buildbot import Build
 from webkitpy.common.net.git_cl import GitCL
 from webkitpy.common.checkout.git_mock import MockGit
@@ skipping 210 matching lines @@
     def test_execute_with_trigger_jobs_option(self):
         return_code = self.command.execute(self.command_options(trigger_jobs=True), [], self.tool)
         self.assertEqual(return_code, 1)
         self.assertLog([
             'INFO: Triggering try jobs for:\n',
             'INFO:   MOCK Try Linux\n',
             'INFO: Please re-run webkit-patch rebaseline-cl once all pending try jobs have finished.\n',
         ])
         self.assertEqual(
             self.tool.executive.calls,
-            [['git', 'cl', 'try', '-b', 'MOCK Try Linux']])
+            [
+                [
+                    'python',
+                    '/mock-checkout/third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt/manifest',
+                    '--work',
+                    '--tests-root',
+                    '/mock-checkout/third_party/WebKit/LayoutTests/external/wpt'
+                ],
+                ['git', 'cl', 'try', '-b', 'MOCK Try Linux']
+            ])
 
     def test_rebaseline_calls(self):
         """Tests the list of commands that are invoked when rebaseline is called."""
         # First write test contents to the mock filesystem so that
         # fast/dom/prototype-taco.html is considered a real test to rebaseline.
         port = self.tool.port_factory.get('test-win-win7')
         self._write(
             port.host.filesystem.join(port.layout_tests_dir(), 'fast/dom/prototype-taco.html'),
             'test contents')
 
@@ skipping 60 matching lines @@
 
     def test_bails_when_there_are_unstaged_baselines(self):
         git = self.tool.git()
         git.unstaged_changes = lambda: {'third_party/WebKit/LayoutTests/my-test-expected.txt': '?'}
         return_code = self.command.execute(self.command_options(), [], self.tool)
         self.assertEqual(return_code, 1)
         self.assertLog([
             'ERROR: Aborting: there are unstaged baselines:\n',
             'ERROR:   /mock-checkout/third_party/WebKit/LayoutTests/my-test-expected.txt\n',
         ])