Add policy for fullscreen mode; disallow fullscreen in public sessions

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 99 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: 236
+#   For your editing convenience: highest ID currently used: 237
 #
 # 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 4062 matching lines @@
 
       When this policy is set, it specifies 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 system tray.
 
       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.''',
     },
     {
+      'name': 'AllowFullscreen',
+      'type': 'main',
+      'schema': { 'type': 'boolean' },
+      'supported_on': ['chrome.*:31-', 'chrome_os:31-'],
+      'features': {
+        'dynamic_refresh': True,
+        'per_profile': True,
+      },
+      'example_value': True,
+      'id': 237,
+      'caption': '''Allow fullscreen mode''',
+      'desc': '''Allow fullscreen mode.

[Mattias Nissler (ping if slow), 2013/08/19 13:29:50]

Can you add a quick summary of what fullscreen mode is?

[bartfab (slow), 2013/08/22 20:21:18]

Done.

+
+      If this policy is set to true or not configured, the user and apps/extensions with appropriate permissions can enter fullscreen mode.

[scheib, 2013/08/19 16:24:08]

This patch is not limiting apps from fullscreen. If that is what you intend to
do you will need to modify ShellWindow / NativeAppWindow* ::*Fullscreen(). Care
must be taken on Mac (maybe ChromeOS) as the window can be made fullscreen
outside of the ShellWindow::Fullscree() method (via titlebar controls -- there's
an outstanding issue to make those work together correctly).

[bartfab (slow), 2013/08/22 20:21:18]

Thanks for the pointers.

Re apps: I extended the CL to prevent apps from using fullscreen as well and
manually tested that the blocking works.

Re Chrome OS: I remember immersive mode added UI elements to the titlebar that
would go directly to fullscreen. These seem to have been removed since. Even
enabling immersive mode via a flag does not bring back the controls. Hence, it
seems that this loophole has been plugged.

Re Mac OS: I was not aware of the fullscreen button. Since the button is not
directly managed by Chrome, working around it would have been tricky. As we do
not need this new policy on Mac right now, I excluded Mac from the list of
platforms that the policy is supported on.

+
+      If this policy is set to false, neither the user nor any apps/extensions can enter fullscreen mode.''',
+    },
+    {
       'name': 'PowerManagement',
       'type': 'group',
       'caption': '''Power mangement''',
       'desc': '''Configure power manegement in <ph name="PRODUCT_OS_NAME">$2<ex>Google Chrome OS</ex></ph>.
 
       These policies let you configure how <ph name="PRODUCT_OS_NAME">$2<ex>Google Chrome OS</ex></ph> behaves when the user remains idle for some amount of time.''',
       'policies': [
         {
           'name': 'ScreenDimDelayAC',
           'type': 'int',
@@ skipping 1332 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': [],
 }