Makes it possible to configure the sources of desktop video stream.

config.js

     bosh: '//jitsi-meet.example.com/http-bind', // FIXME: use xep-0156 for that
     desktopSharing: 'ext', // Desktop sharing method. Can be set to 'ext', 'webrtc' or false to disable.
     chromeExtensionId: 'diibjkoicjeejcmhdnailmkgecihlobk', // Id of desktop streamer Chrome extension
+    desktopSharingSources: ['screen', 'window'],
     minChromeExtVersion: '0.1', // Required version of Chrome extension
     enableRtpStats: true, // Enables RTP stats processing
     openSctp: true, // Toggle to enable/disable SCTP channels

desktopsharing.js

     // Sends 'getStream' msg to the extension. Extension id must be defined in the config.
     chrome.runtime.sendMessage(
         config.chromeExtensionId,
-        { getStream: true},
+        { getStream: true, sources: config.desktopSharingSources },
         function (response) {
             if (!response) {
                 failCallback(chrome.runtime.lastError);