Add policy for ash launcher auto-hide behavior

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: 165
+#   For your editing convenience: highest ID currently used: 166
 #
 # 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 3187 matching lines @@
       'id': 165,
       'caption': '''Use built-in DNS client''',
       'desc': '''Controls whether the built-in DNS client is used in <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>.
 
       If this policy is set to true, the built-in DNS client will be used, if available.
 
       If this policy is set to false, the built-in DNS client will never be used.
 
       If this policy is left not set, the users will be able to change whether the built-in DNS client is used by editing chrome://flags or specifying a command-line flag.''',
     },
+    {
+      'name': 'ShelfAutoHideBehavior',
+      'type': 'string-enum',

[Mattias Nissler (ping if slow), 2012/11/30 12:07:15]

Is there a good reason not to make this a boolean?

[bartfab (slow), 2012/11/30 12:13:47]

The reason is that it can be trivially added to
configuration_policy_handler_list and translates directly into the corresponding
pref. I can make it a bool and translate in a few lines of code instead of
course.

[Mattias Nissler (ping if slow), 2012/11/30 12:17:40]

I would prefer the bool unless we have indication there's a chance the shelf
code adds additional enum constants. Do you know? If the authors are actually
keeping that option open, we should probably be defensive and keep the enum.

[sky, 2012/11/30 17:37:37]

Originally we had three values hence the enum, now we're at two. I prefer a
string value pref in the chrome side of things as it gives more flexibility and
is less error prone when migrating. Additionally the UX folks have frequently
gone back and forth in this area. That said, I'm not sure how this code maps to
the prefs or if compatibility matters here. If it's trivial to convert from
boolean->string or string->bool and you don't have to worry about backwards
compatibility then go for the bool.

[Mattias Nissler (ping if slow), 2012/11/30 17:39:04]

Thanks Scott for the background information. We have to worry about backwards
compatibility unfortunately. An enum it is then.

+      'schema': {
+        'type': 'string',
+        'enum': [
+          'Always',
+          'Never'
+        ],
+      },
+      'items': [
+        {
+          'name': 'AlwaysAutoHideShelf',
+          'value': 'Always',
+          'caption': '''Always auto-hide the shelf''',
+        },
+        {
+          'name': 'NeverAutoHideShelf',
+          'value': 'Never',
+          'caption': '''Never auto-hide the shelf''',
+        },
+      ],
+      'supported_on': ['chrome_os:25-'],
+      'features': {
+        'dynamic_refresh': True,
+        'can_be_recommended': True,
+      },
+      'example_value': 'Always',
+      'id': 166,
+      'caption': '''Control shelf auto-hiding''',
+      '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.''',
+    },
   ],
   '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 78 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': [],
 }