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

chrome/common/extensions/api/privacy.json

Index: chrome/common/extensions/api/privacy.json
diff --git a/chrome/common/extensions/api/privacy.json b/chrome/common/extensions/api/privacy.json
index e3f71de7b3cbb8d125ecd5103861725827559f84..87cf495e1cafcb133de14c7cb66f30520bfd6312 100644
--- a/chrome/common/extensions/api/privacy.json
+++ b/chrome/common/extensions/api/privacy.json
@@ -16,6 +16,11 @@
             "$ref": "types.ChromeSetting",
             "value": ["networkPredictionEnabled", {"type":"boolean"}],
             "description": "If enabled, Chrome attempts to speed up your web browsing experience by pre-resolving DNS entries, prerendering sites (<code>&lt;link rel='prefetch' ...&gt;</code>), and preemptively opening TCP and SSL connections to servers.  This preference's value is a boolean, defaulting to <code>true</code>."
+          },
+          "webRTCMultipleRoutesEnabled": {
+            "$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.

           }
         }
       },