Allow recommended locales to be set for public sessions

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 47f26f60d38f5d3c239b46bb5e8370fba5fbee04..fec9226fbe1359330930e4b8b954fc19feebcaee 100644
--- a/components/policy/resources/policy_templates.json
+++ b/components/policy/resources/policy_templates.json
@@ -120,7 +120,7 @@
 #   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: 270
+#   For your editing convenience: highest ID currently used: 271
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
@@ -6528,6 +6528,42 @@
       While the policy itself is supported on the above platforms, the feature it is enabling may be available on fewer platforms. Not all deprecated Web Platform features can be re-enabled. Only the ones explicitly listed below can be for a limited period of time, which is different per feature. The general format of the string tag will be [DeprecatedFeatureName]_EffectiveUntil[yyyymmdd]. As reference, you can find the intent behind the Web Platform feature changes at http://bit.ly/blinkintents.
       ''',
     },
+    {
+      'name': 'SessionLocales',
+      'type': 'list',
+      'schema': {
+        'type': 'array',
+        'items': { 'type': 'string' },
+      },
+      'supported_on': ['chrome_os:38-'],
+      'features': {
+        'can_be_recommended': True,
+        'dynamic_refresh': True,
+        'per_profile': True,
+      },
+      'example_value': ['de', 'fr'],
+      'id': 271,
+      'caption': '''Set the recommended locales for a public session''',
+      'desc': '''Sets one or more recommended locales for a public sessions, allowing users to easily choose one of these locales.
+
+      The user can choose a locale and a keyboard layout before starting a public session. By default, all locales supported by <ph name="PRODUCT_OS_NAME">$2<ex>Google Chrome OS</ex></ph> are listed in alphabetic order. You can use this policy to move a set of recommended locales to the top.
+
+      If this policy is set, the recommended locales will be moved to the top of the list and will be visually separated from all other locales. The first recommended locale will be pre-selected.
+
+      If this policy is not set, the current UI locale will be pre-selected.

[pneubeck (no reviews), 2014/07/30 15:23:19]

Maybe more clearly partition this description into the following parts:

- Short summary (current line 6547)
- Behavior independent of policy (lines 6549 without last sentence, 6555)
- Behavior without the policy (line 6553)
- Behavior with the policy (last sentence of 6549, lines 6557-6561)
- Additional notes (line 6563)

[bartfab (slow), 2014/08/05 17:16:24]

Done.

+
+      The pre-selected keyboard layout will be the most popular layout matching the selected locale.
+
+      If there is more than one recommended locale, it is assumed that users will want to select among these locales. Locale and keyboard layout selection is prominently offered when starting a public session.

[pneubeck (no reviews), 2014/07/30 15:23:19]

In which order are the recommended locales shown? Alphabetically or as set in
the policy?

[bartfab (slow), 2014/08/05 17:16:24]

Clarified.

+
+      If there is no or only one recommended locale, it is assumed that most users will want to use the pre-selected locale. Locale and keyboard layout selection is less prominently offered when starting a public session.

[pneubeck (no reviews), 2014/07/30 15:23:19]

'no or' implies that setting an empty list of recommended locales is supported.
In line 6547 it says 'one or more'.

Maybe mention the empty list only as an 'error' which will be ignored?

[bartfab (slow), 2014/08/05 17:16:24]

Recommending an empty list works but makes little sense as it is equivalent to
no recommendation at all. I simplified this sentence by using "Otherwise,". I
intentionally prefer not to go into a lengthy description of what happens when
there is an empty recommended list. Chrome will handle it 100% gracefully and
correctly but there is no point in setting an empty list, so I would rather not
complicate the policy description further with this corner case.

+
+      When this policy is set and automatic login is enabled (see the |DeviceLocalAccountAutoLoginId| and |DeviceLocalAccountAutoLoginDelay| policies), the automatically started public session will use the first recommended locale and the most popular keyboard layout matching this locale.

[pneubeck (no reviews), 2014/07/30 15:23:19]

The second half of the last sentence is redundant to line 6555.
Maybe drop?

[bartfab (slow), 2014/08/05 17:16:24]

No, it's not redundant. Line 6555 explains what keyboard layout will be
pre-selected for users going through the manual login flow. This sentence
describes what keyboard layout Chrome will pick automatically during auto-login.

+
+      This policy can only be set as recommended. You can use this policy to move a set of recommended locales to the top but users are always allowed to choose any locale supported by <ph name="PRODUCT_OS_NAME">$2<ex>Google Chrome OS</ex></ph> for their session.

[pneubeck (no reviews), 2014/07/30 15:23:19]

Hm. So we don't have a 'features' flag to declare 'can_be_mandatory':false ?

[bartfab (slow), 2014/08/05 17:16:24]

Correct, there is no such flag. It is not needed for now because at the moment,
the only two policies that do not support mandatory are for Chrome OS, where the
policy templates auto-generated from this file are not used. Once we get the
first policy that does not support mandatory on desktop, we should add a flag.

+      ''',
+    },
+
   ],
   'messages': {
     # Messages that are not associated to any policies.