Add policy to control valid UDP port range in WebRTC

components/policy/resources/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 119 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: 338
+#   For your editing convenience: highest ID currently used: 339
 #
 # 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 8637 matching lines @@
       },
       'example_value': True,
       'id': 338,
       'caption': '''Show content suggestions on the New Tab page''',
       'tags': [],
       'desc':
       '''If this is set to true or not set, the New Tab page may show content suggestions based on the user's browsing history, interests, or location.
 
       If this is set to false, automatically-generated content suggestions are not shown on the New Tab page.''',
     },
+    {
+      'name': 'WebRtcUdpPortRange',
+      'type': 'string',
+      'schema': { 'type': 'string' },
+      'supported_on': ['chrome.*:54-', 'chrome_os:54-'],
+      'features': {
+        'dynamic_refresh': False,
+        'per_profile': True,
+      },
+      'example_value': '10000-11999',
+      'id': 339,
+      'caption': '''Restrict the UDP port range used by WebRTC''',
+      'tags': [],
+      'desc': '''Restricts the UDP port range used by WebRTC in this machine.

[Thiemo Nagel, 2016/08/11 09:29:26]

Nit: I'm not in favour of duplicating the caption in the description (although
there is ample precedent for it).

[Guido Urdaneta, 2016/08/11 10:10:25]

Done.

[Thiemo Nagel, 2016/08/11 10:22:31]

As a second thought, I think it would be better spell out what the policy does a
bit more explicitly, eg.: "If the policy is set, the UDP port range used by
WebRTC is restricted to the specified port interval (endpoints included)."

[Guido Urdaneta, 2016/08/11 10:31:19]

Done.

+
+      If this policy is left not set, or if it is set to an empty string or an invalid port range, WebRTC will be allowed to use any available port.''',

[Thiemo Nagel, 2016/08/11 09:29:26]

Nit: In my opinion present tense is better style.

[Guido Urdaneta, 2016/08/11 10:10:25]

Done.

[Thiemo Nagel, 2016/08/11 10:22:32]

Optional nit: Actually it's still future tense. ;)

[Guido Urdaneta, 2016/08/11 10:31:19]

Done. I originally thought you meant you didn't like passive voice :)

+    },
   ],
   '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 Chromium are being edited''',
       'text': '''<ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> preferences'''
@@ skipping 109 matching lines @@
       '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)',
     },
     'doc_complex_policies_on_windows': {
       'desc': '''Text pointing the user to a help article for complex policies on Windows''',
       'text': '''encoded as a JSON string, for details see <ph name="COMPLEX_POLICIES_URL">https://www.chromium.org/administrators/complex-policies-on-windows<ex>https://www.chromium.org/administrators/complex-policies-on-windows</ex></ph>''',
     },
   },
   'placeholders': [],
 }