Add policy for fullscreen mode; disallow fullscreen in public sessions

chrome/app/policy/policy_templates.json

Index: chrome/app/policy/policy_templates.json
diff --git a/chrome/app/policy/policy_templates.json b/chrome/app/policy/policy_templates.json
index 10ad804e04cdcec44eaee5438caa82435b799671..9e86fe65466fbb92d4feac9cafd34a5864140515 100644
--- a/chrome/app/policy/policy_templates.json
+++ b/chrome/app/policy/policy_templates.json
@@ -117,7 +117,7 @@
 #   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: 236
+#   For your editing convenience: highest ID currently used: 237
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
@@ -4200,6 +4200,24 @@
       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''',