Add policy for limiting the session length

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 94 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: 168
+#   For your editing convenience: highest ID currently used: 169
 #
 # 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 3683 matching lines @@
       'desc': '''Control auto-hiding of the <ph name="PRODUCT_OS_NAME">$2<ex>Google Chrome OS</ex></ph> shelf.
 
       If this policy is set to 'AlwaysAutoHideShelf', the shelf will always auto-hide.
 
       If this policy is set to 'NeverAutoHideShelf', the shelf never auto-hide.
 
       If you set this policy, users cannot change or override it.
 
       If the policy is left not set, users can choose whether the shelf should auto-hide.''',
     },
+    {
+      'name': 'SessionLengthLimit',
+      'type': 'int',
+      'schema': { 'type': 'integer' },
+      'supported_on': ['chrome_os:25-'],
+      'features': {
+        'dynamic_refresh': True,
+        'per_profile': False,
+      },
+      'example_value': 3600000,
+      'id': 169,
+      'caption': '''Limit the session length''',
+      'desc': '''Limit the maximum length of a user session.
+
+      When this policy is set, it specifies the the length of time after which a user is automatically logged out, terminating the session. The user is informed about the remaining time by a countdown timer shown in the ash system tray.

[Mattias Nissler (ping if slow), 2012/12/12 10:12:57]

s/the the/the/
Remove "ash"? People don't know what ash is, system tray is probably good
enough. What wording do we use elsewhere?

[bartfab (slow), 2012/12/13 16:22:48]

"the the" - Done.
"ash" - Done. There was one other policy that referred to the "ash system tray".
I replaced the term with just "system tray" there as well.

+
+      When this policy is not set, the session length is not limited.
+
+      If you set this policy, users cannot change or override it.
+
+      The policy value should be specified in milliseconds. Values are clamped to a range of 30 seconds to 24 hours.''',
+    },
   ],
   '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''',
       'text': '''<ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> preferences'''
@@ skipping 82 matching lines @@
       'desc': '''Text appended in parentheses to the policy name to indicate that it has been deprecated''',
       'text': 'deprecated',
     },
     'doc_recommended': {
       '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)',
     },
   },
   'placeholders': [],
 }