Add WPTManifest log line to diagnose slow manifest generation

third_party/WebKit/Tools/Scripts/webkitpy/w3c/wpt_manifest.py

 # Copyright 2017 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.
 
 """WPTManifest is responsible for handling MANIFEST.json.
 
 The MANIFEST.json file contains metadata about files in web-platform-tests,
 such as what tests exist, and extra information about each test, including
 test type, options, URLs to use, and reference file paths if applicable.
 """
@@ skipping 87 matching lines @@
             _log.error('Manifest base not found at "%s".', base_manifest_path)
             host.filesystem.write_text_file(base_manifest_path, '{}')
 
         if not host.filesystem.exists(manifest_path):
             _log.debug('Manifest not found, copying from base "%s".', base_manifest_path)
             host.filesystem.copyfile(base_manifest_path, manifest_path)
 
         wpt_path = manifest_path = finder.path_from_layout_tests('external', 'wpt')
         WPTManifest.generate_manifest(host, wpt_path)
 
+        # Adding this log line to diagnose https://crbug.com/714503
+        _log.debug('Manifest generation completed.')
+
     @staticmethod
     def generate_manifest(host, dest_path):
         """Generates MANIFEST.json on the specified directory."""
         executive = host.executive
         finder = WebKitFinder(host.filesystem)
         manifest_exec_path = finder.path_from_tools_scripts('webkitpy', 'thirdparty', 'wpt', 'wpt', 'manifest')
 
         cmd = ['python', manifest_exec_path, '--work', '--tests-root', dest_path]
         _log.debug('Running command: %s', ' '.join(cmd))
         proc = executive.popen(cmd, stdout=executive.PIPE, stderr=executive.PIPE, stdin=executive.PIPE, cwd=finder.webkit_base())
         out, err = proc.communicate('')
         if proc.returncode:
             _log.info('# ret> %d', proc.returncode)
             if out:
                 _log.info(out)
             if err:
                 _log.info(err)
             host.exit(proc.returncode)
         return proc.returncode, out