Add a device policy for specifying the release channel.

chrome/app/policy/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 76 matching lines @@
 #   policy configuration files. 'dynamic_refresh' controls if the generated
 #   documentation should state that the policy supports dynamic refresh or not.
 #   Supporting dynamic refresh means that Chrome respects the changes to the
 #   policy immediately, without the need for restart.
 #
 # 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: 90
+#   For your editing convenience: highest ID currently used: 91
 #
 # 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
 #
 # Device Policy:
 #   An additional flag device_only (optional, defaults to False) indicates
@@ skipping 1450 matching lines @@
       'supported_on': ['chrome_os:1.0-'],
       'device_only': True,
       'features': {'dynamic_refresh': 1},
       'example_value': 3600000,
       'id': 90,
       'caption': '''Refresh rate for Device Policy''',
       'desc': '''Specifies the period in milliseconds at which the device management service is queried for device policy information.
 
       Setting this policy overrides the default value of 3 hours. Valid values for this policy are in the range from 1800000 (30 minutes) to 86400000 (1 day). Any values not in this range will be clamped to the respective boundary.''',
     },
+    {
+      'name': 'ChromeOsReleaseChannel',
+      'type': 'string-enum',
+      'items': [
+        {
+          'name': 'Stable',
+          'value': 'stable-channel',
+          'caption': '''Stable channel'''
+        },
+        {
+          'name': 'Beta',
+          'value': 'beta-channel',
+          'caption': '''Beta channel'''
+        },
+        {
+          'name': 'Dev - Unstable',
+          'value': 'dev-channel',
+          'caption': '''Dev channel (may be unstable)'''
+        }
+      ],
+      'supported_on': ['chrome_os:1.0-'],
+      'device_only': True,
+      'features': {'dynamic_refresh': 1},
+      'example_value': 'stable-channel',
+      'id': 91,
+      'caption': '''Release channel''',
+      'desc': '''Specifies the release channel that this device should be locked to. This policy is a work in progress; currently, the user can still change the release channel even if it's specified by the policy.'''
+    },
 
   ],
   'messages': {
     # Messages that are not associated to any policies.
     'win_supported_winxpsp2': {
       'desc': '''A label specifying the oldest possible compatible version of Windows. This text will appear right next to a label containing the text 'Supported on:'.''',
       'text': '''Microsoft Windows XP SP2 or later'''
     },
     'mac_chrome_preferences': {
       'desc': '''A text indicating in Mac OS X Workgroup Manager, that currently the preferences of Chrome are being edited''',
@@ skipping 71 matching lines @@
       'desc': '''The name of the feature that indicates for a given policy that changes to it are respected by Chrome without a browser restart''',
       'text': '''Dynamic Policy Refresh'''
     },
     'doc_deprecated': {
       'desc': '''Text appended in parentheses to the policy name to indicate t hat it has been deprecated''',
       'text': 'deprecated',
     }
   },
   'placeholders': [],
 }