Add `privacy.network.webRTCMultipleRoutesEnabled` to extensions API.

chrome/common/extensions/api/privacy.json

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
   {
     "namespace": "privacy",
     "description": "Use the <code>chrome.privacy</code> API to control usage of the features in Chrome that can affect a user's privacy. This API relies on the <a href='types#ChromeSetting'>ChromeSetting prototype of the type API</a> for getting and setting Chrome's configuration.",
     "properties": {
       "network": {
         "type": "object",
         "value": {},
         "description": "Settings that influence Chrome's handling of network connections in general.",
         "properties": {
           "networkPredictionEnabled": {
             "$ref": "types.ChromeSetting",
             "value": ["networkPredictionEnabled", {"type":"boolean"}],
             "description": "If enabled, Chrome attempts to speed up your web browsing experience by pre-resolving DNS entries, prerendering sites (<code>&lt;link rel='prefetch' ...&gt;</code>), and preemptively opening TCP and SSL connections to servers.  This preference's value is a boolean, defaulting to <code>true</code>."
+          },
+          "webRTCMultipleRoutesEnabled": {
+            "$ref": "types.ChromeSetting",
+            "value": ["webRTCMultipleRoutesEnabled", {"type":"boolean"}],
+            "description": "If enabled, Chrome will explore all possible routing options when using WebRTC. This preference's value is a boolean, defaulting to <code>true</code>."

[msramek, 2015/02/19 10:28:36]

I would avoid awkward phrasing "You can only enable this preference if WebRTC
itself is enabled..."

- On Android, you can disable WebRTC through about://flags, but Clank doesn't
support extensions anyway
- On other OS, you can't disable it through about://flags
- WebRTC team is planning to remove the ENABLE_WEBRTC flag soon anyway

I think that it's not necessary to mention.

[Mike West, 2015/02/19 10:37:18]

I don't think that's necessary to mention, but I do think you should mention
something about the impact of the setting. That is, what does "explore all
possible routing options" mean? How does that have a privacy impact? If anything
it sounds like turning it _off_ would be the right thing to do from a privacy
perspective, but I think that's incorrect, isn't it?

[msramek, 2015/02/19 10:51:47]

It's correct :) The flag is _on_ by default (needed for WebRTC's performance)
and we provide the possibility to turn it off for privacy-concerned users.

PTAL.

           }
         }
       },
       "services": {
         "type": "object",
         "value": {},
         "description": "Settings that enable or disable features that require third-party network services provided by Google and your default search provider.",
         "properties": {
           "alternateErrorPagesEnabled": {
             "$ref": "types.ChromeSetting",
@@ skipping 66 matching lines @@
             "$ref": "types.ChromeSetting",
             "value": ["protectedContentEnabled", {"type":"boolean"}],
             "description": "<strong>Available on Windows and ChromeOS only</strong>: If enabled, Chrome provides a unique ID to plugins in order to run protected content. The value of this preference is of type boolean, and the default value is <code>true</code>.",
             "platforms": ["windows", "cros", "cros touch"]
           }
         }
       }
     }
   }
 ]