Functionality to allow blacklist and whitelist of custom schemes

components/policy/resources/policy_templates.json

 {
 # policy_templates.json - Metafile for policy templates
 #
 # The content of this file is evaluated as a Python expression.
 #
 # This file is used as input to generate the following policy templates:
 # ADM, ADMX+ADML, MCX/plist and html documentation.
 #
 # Policy templates are user interface definitions or documents about the
 # policies that can be used to configure Chrome. Each policy is a name-value
@@ skipping 4286 matching lines @@
         'chrome.*:15-',
         'chrome_os:15-',
         'android:30-',
         'webview_android:47-',
         'ios:34-47',
       ],
       'features': {
         'dynamic_refresh': True,
         'per_profile': True,
       },
-      'example_value': ['example.com', 'https://ssl.server.com', 'hosting.com/bad_path', 'https://server:8080/path', '.exact.hostname.com', 'file://*', '*'],
+      'example_value': ['example.com', 'https://ssl.server.com', 'hosting.com/bad_path', 'https://server:8080/path', '.exact.hostname.com', 'file://*', 'custom_scheme:*', '*'],
       'id': 103,
       'caption': '''Block access to a list of URLs''',
       'tags': ['filtering'],
       'desc': '''Blocks access to the listed URLs.
 
       This policy prevents the user from loading web pages from blacklisted URLs. The blacklist provides a list of URL patterns that specify which URLs will be blacklisted.
 
-      Each URL pattern can either be a pattern for local files or a generic URL pattern. Local file patterns are of the format 'file://path', where path should be an absolute path to block. All file system locations for which that path is a prefix will be blocked.
-
-      A generic URL pattern has the format 'scheme://host:port/path'.
-      If present, only the specified scheme will be blocked. If the scheme:// prefix is not specified, all schemes are blocked.
-      The host is required and can be a hostname or an IP address. Subdomains of a hostname will also be blocked. To prevent blocking subdomains, include a '.' before the hostname. The special hostname '*' will block all domains.
-      The optional port is a valid port number from 1 to 65535. If none is specified, all ports are blocked.
-      If the optional path is specified, only paths with that prefix will be blocked.
+      A URL pattern has to be formatted according to https://www.chromium.org/administrators/url-blacklist-filter-format.
 
       Exceptions can be defined in the URL whitelist policy. These policies are limited to 1000 entries; subsequent entries will be ignored.
 
       Note that it is not recommended to block internal 'chrome://*' URLs since this may lead to unexpected errors.
 
       If this policy is not set no URL will be blacklisted in the browser.''',
     },
     {
       'name': 'URLWhitelist',
       'type': 'list',
@@ skipping 4341 matching lines @@
       'desc': '''Text appended in parentheses next to the policies top-level container to indicate that those policies are of the Recommended level''',
       'text': 'Default Settings (users can override)',
     },
     'doc_complex_policies_on_windows': {
       'desc': '''Text pointing the user to a help article for complex policies on Windows''',
       'text': '''encoded as a JSON string, for details see <ph name="COMPLEX_POLICIES_URL">https://www.chromium.org/administrators/complex-policies-on-windows<ex>https://www.chromium.org/administrators/complex-policies-on-windows</ex></ph>''',
     },
   },
   'placeholders': [],
 }