Add a policy to always show the Cast toolbar icon

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 121 matching lines @@
 #   templates and documentation. The policy definition list that Chrome sees
 #   will include policies marked with 'future'. If a WIP policy isn't meant to
 #   be seen by the policy providers either, the 'supported_on' key should be set
 #   to an empty list.
 #
 # IDs:
 #   Since a Protocol Buffer definition is generated from this file, unique and
 #   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: 361
+#   For your editing convenience: highest ID currently used: 362
 #   And don't forget to also update the EnterprisePolicies enum of
 #   histograms.xml.
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
 #     $1 -> Google Chrome / Chromium
 #     $2 -> Google Chrome OS / Chromium OS
 #     $3 -> Google Chrome Frame / Chromium Frame
 #     $6 is reserved for doc_writer
 #
@@ skipping 8985 matching lines @@
 
       This defaults to True (security feature enabled), except for Chrome OS
       enterprise users for which this currently defaults to False.
 
       It is recommended that this be set to True. The only reason to set it to
       False is if it causes a compatibility problem with existing PAC scripts.
 
       The desire is to remove this override in the future.''',
     },
     {
-      'name': 'EnableMediaRouter',
-      'type': 'main',
-      'schema': { 'type': 'boolean' },
-      'supported_on': ['chrome.*:52-', 'chrome_os:52-', 'android:52-'],
-      'features': {
-        'dynamic_refresh': False,
-        'per_profile': True,
-      },
-      'example_value': True,
-      'id': 333,
-      'caption': '''Enables cast''',
-      'tags': [],
-      'desc': '''If this is set to true or is not set, users will be able to cast tabs, sites or the desktop from the browser. If set to false, this option will be disabled.'''
+      'name': 'GoogleCast',
+      'type': 'group',
+      'caption': '''Google Cast''',
+      'desc': '''Configure policies for Google Cast, a feature that allows users to send the contents of tabs, sites or the desktop from the browser to remote displays and sound systems.''',
+      'policies': [
+        {
+          'name': 'EnableMediaRouter',
+          'type': 'main',
+          'schema': { 'type': 'boolean' },
+          'supported_on': ['chrome.*:52-', 'chrome_os:52-', 'android:52-'],
+          'features': {
+            'dynamic_refresh': False,
+            'per_profile': True,
+          },
+          'example_value': True,
+          'id': 333,
+          'caption': '''Enables Google Cast''',
+          'tags': [],
+          'desc': '''If this policy is set to true or is not set, Google Cast will be enabled, and users will be able to launch it from the app menu, page context menus, media controls on Cast-enabled websites, and (if shown) the Cast toolbar icon.
+
+          If this policy set to false, Google Cast will be disabled.'''
+        },
+        {
+          'name': 'ShowCastIconInToolbar',
+          'type': 'main',
+          'schema': { 'type': 'boolean' },
+          'supported_on': ['chrome.*:58-', 'chrome_os:58-'],
+          'features': {
+            'dynamic_refresh': False,
+            'per_profile': True,
+          },
+          'example_value': False,
+          'id': 362,
+          'caption': '''Shows the Google Cast toolbar icon''',
+          'tags': [],
+          'desc': '''If this policy is set to true, the Cast toolbar icon will always be shown on the toolbar or the overflow menu, and users will not be able to remove it.
+
+          If this policy is set to false or is not set, users will be able to pin or remove the icon via its contextual menu.
+
+          If the policy "EnableMediaRouter" is set to false, then this policy's value would have no effect, and the toolbar icon would not be shown.'''
+        },
+      ],
     },
     {
       'name': 'ArcBackupRestoreEnabled',
       'type': 'main',
       'schema': { 'type': 'boolean' },
       'supported_on': ['chrome_os:53-'],
       'features': {
         'dynamic_refresh': True,
         'per_profile': False,
       },
@@ skipping 449 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': [],
 }