Point to build requirements page when there is a dependency check failure.

Tools/Scripts/webkitpy/layout_tests/port/mac.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 41 matching lines @@
     FALLBACK_PATHS['mavericks'] = ['mac']
     FALLBACK_PATHS['mountainlion'] = ['mac-mountainlion'] + FALLBACK_PATHS['mavericks']
     FALLBACK_PATHS['retina'] = ['mac-retina'] + FALLBACK_PATHS['mountainlion']
     FALLBACK_PATHS['lion'] = ['mac-lion'] + FALLBACK_PATHS['mountainlion']
     FALLBACK_PATHS['snowleopard'] = ['mac-snowleopard'] + FALLBACK_PATHS['lion']
 
     DEFAULT_BUILD_DIRECTORIES = ('xcodebuild', 'out')
 
     CONTENT_SHELL_NAME = 'Content Shell'
 
+    BUILD_REQUIREMENTS_URL = 'https://code.google.com/p/chromium/wiki/MacBuildInstructions'
+
     @classmethod
     def determine_full_port_name(cls, host, options, port_name):
         if port_name.endswith('mac'):
             if host.platform.os_version in ('future',):
                 version = 'mavericks'
             else:
                 version = host.platform.os_version
             if host.platform.is_highdpi():
                 version = 'retina'
             return port_name + '-' + version
@@ skipping 47 matching lines @@
     def _path_to_driver(self, configuration=None):
         # FIXME: make |configuration| happy with case-sensitive file systems.
         return self._build_path_with_configuration(configuration, self.driver_name() + '.app', 'Contents', 'MacOS', self.driver_name())
 
     def _path_to_helper(self):
         binary_name = 'layout_test_helper'
         return self._build_path(binary_name)
 
     def _path_to_wdiff(self):
         return 'wdiff'