Add policy to control valid UDP port range in WebRTC

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 177040f1c64a39a8775efbcbb5b09639d9f32653..22d73891638a6a647d22797991185c8dcd54f9f0 100644
--- a/components/policy/resources/policy_templates.json
+++ b/components/policy/resources/policy_templates.json
@@ -137,7 +137,7 @@
 #   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: 336
+#   For your editing convenience: highest ID currently used: 337
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
@@ -8743,6 +8743,23 @@
       'tags': [],
       'desc': '''If this is set to true or is not set, users will be able to cast tabs, sites or the desktop from the browser. If set to false, this option will be disabled.'''
     },
+    {
+      'name': 'WebRtcUdpPortRange',
+      'type': 'string',
+      'schema': { 'type': 'string' },
+      'supported_on': ['chrome.*:54-', 'chrome_os:54-'],
+      'features': {
+        'dynamic_refresh': False,
+        'per_profile': True,
+      },
+      'example_value': '10400-10409',

[tommi (sloooow) - chröme, 2016/07/06 10:46:43]

nit: as an example, we might want to have a wider range.  Incidentally, have you
tested what happens if the range is set to be very small and you run an app such
as Hangouts?

[Guido Urdaneta, 2016/07/07 09:27:55]

Actually, it is not working as we expected since IPCPacketSocketFactory 
currently ignores port limits.
https://cs.chromium.org/chromium/src/content/renderer/p2p/ipc_socket_factory....

We'll have to fix that before landing this CL.

[Guido Urdaneta, 2016/07/11 17:18:37]

I tested this on top of an updated IpcSocketFactory and once Hangouts runs out
of UDP ports it starts using TCP.

+      'id': 337,
+      'caption': '''Restrict the UDP port range used by WebRTC''',
+      'tags': [],
+      'desc': '''Restricts the UDP port range used by WebRTC in this machine.
+
+      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.''',
+    },
   ],
   'messages': {
     # Messages that are not associated to any policies.