Enable policy support for registering protocol handler.

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 c6f0a430d72b11e2399a0915d90f2d1d5fcd890e..a384c8365ccd47e3b417f3d2ab307e9373e3b863 100644
--- a/components/policy/resources/policy_templates.json
+++ b/components/policy/resources/policy_templates.json
@@ -118,7 +118,7 @@
 #   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: 267
+#   For your editing convenience: highest ID currently used: 268
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
@@ -2668,6 +2668,42 @@
           If this policy is left not set the global default value will be used for all sites either from the 'DefaultPopupsSetting' policy if it is set, or the user's personal configuration otherwise.''',
         },
         {
+          'name': 'RegisteredProtocolHandlers',
+          'type': 'list',
+          'schema': {
+            'type': 'array',
+            'items': {
+              'type': 'object',
+              'properties': {
+                'default': {
+                  'description': 'A boolean flag indicating if the protocol handler should be set as the default.',
+                  'type': 'boolean'
+                },
+                'protocol': {
+                  'description': 'The protocol for the protocol handler.',
+                  'type': 'string'
+                },
+                'url': {
+                  'description': 'The URL of the protocol handler.',
+                  'type': 'string'
+                }
+              },
+              'required': ['protocol', 'url']
+            }
+          },
+          'supported_on': ['chrome.*:37-', 'chrome_os:37-'],
+          'features': {
+            'dynamic_refresh': False,
+            'per_profile': True,
+          },
+          'example_value': [{'protocol': 'mailto', 'url': 'https://mail.google.com/mail/?extsrc=mailto&url=%s'}],
+          'id': 268,
+          'caption': '''Register protocol handlers''',
+          'desc': '''Allows you to register a list of protocol handlers. This can only be a recommended policy. The field |protocol| should be set to the scheme such as 'mailto' and the field |url| should be set to the URL pattern of the application that handles the scheme. The pattern should include a '%s' as a placeholder for data.
+
+          The protocol handlers registered by policy are merged with the ones registered by the user via settings and both are available for use. The user can override the protocol handlers installed by policy by installing a new default handler, but is not allowed to remove a protocol handler registered by policy.''',
+        },
+        {
           'name': 'PopupsBlockedForUrls',
           'type': 'list',
           'schema': {