Implement Web Restrictions in WebView.

components/policy/resources/policy_templates.json

Index: components/policy/resources/policy_templates.json
diff --git a/components/policy/resources/policy_templates.json b/components/policy/resources/policy_templates.json
index 2751effe1c548bb95912cd0ea499cce7a11effa6..306e7f7d6e2e59acf41ea8eb72a35f5a07e784b3 100644
--- a/components/policy/resources/policy_templates.json
+++ b/components/policy/resources/policy_templates.json
@@ -137,7 +137,7 @@
 #   persistent IDs for all fields (but not for groups!) are needed. These are
 #   specified by the 'id' keys of each policy. NEVER CHANGE EXISTING IDs,
 #   because doing so would break the deployed wire format!
-#   For your editing convenience: highest ID currently used: 338
+#   For your editing convenience: highest ID currently used: 339
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
@@ -8795,6 +8795,21 @@
 
       If this is set to false, automatically-generated content suggestions are not shown on the New Tab page.''',
     },
+    {
+      'name': 'WebRestrictionsAuthority',
+      'id': 339,
+      'type': 'string',
+      'schema' : { 'type': 'string' },
+      'tags': ['filtering'],
+      'supported_on': ['webview_android:54-'],
+      'caption': '''Set an external source of URL restrictions''',
+      'desc' : '''When this policy is set to a non-empty string the WebView will read URL restrictions from the content provider with the given authority name.''',
+      'features': {
+        'dynamic_refresh': True,
+        'per_profile': False,
+      },
+      'example_value': 'com.android.chrome.SupervisedUserProvider'
+    },
   ],
   'messages': {
     # Messages that are not associated to any policies.