cleanup: Make desktop sharing options consistent and drop deprecated ones

Make sure there are options to set the extension ID and an enabled flag for
both Chrome and Firefox.

Removed checking for deprecated configuration options: desktopSharing,
chromeExtensionId and minChromeExtVersion.

doc/API.md

 *  ```JitsiMeetJS.init(options)``` - this method initialized Jitsi Meet API.
 The ```options``` parameter is JS object with the following properties:
     1. useIPv6 - boolean property
-    2. desktopSharingChromeMethod - Desktop sharing method. Can be set to 'ext', 'webrtc' or false to disable.
-    3. desktopSharingChromeExtId - The ID of the jidesha extension for Chrome or Firefox. Example: 'mbocklcggfhnbahlnepmldehdhpjfcjp'
-    desktopSharingChromeSources - Array of strings with the media sources to use when using screen sharing with the Chrome extension. Example: ['screen', 'window']
-    4. desktopSharingChromeMinExtVersion - Required version of Chrome extension. Example: '0.1'
-    5. desktopSharingFirefoxExtId - The ID of the jidesha extension for Firefox. If null, we assume that no extension is required.
-    6. desktopSharingFirefoxDisabled - Boolean. Whether desktop sharing should be disabled on Firefox. Example: false.
-    7. desktopSharingFirefoxMaxVersionExtRequired - The maximum version of Firefox which requires a jidesha extension. Example: if set to 41, we will require the extension for Firefox versions up to and including 41. On Firefox 42 and higher, we will run without the extension. If set to -1, an extension will be required for all versions of Firefox.
-    8. desktopSharingFirefoxExtensionURL - The URL to the Firefox extension for desktop sharing. "null" if no extension is required.
-    9. disableAudioLevels - boolean property. Enables/disables audio levels.
-    10. disableSimulcast - boolean property. Enables/disables simulcast.
-    11. enableWindowOnErrorHandler - boolean property (default false). Enables/disables attaching global onerror handler (window.onerror).
-    12. disableThirdPartyRequests - if true - callstats will be disabled and the callstats API won't be included.
-    13. enableAnalyticsLogging - boolean property (default false). Enables/disables analytics logging.
-    14. callStatsCustomScriptUrl - (optional) custom url to access callstats client script
-    15. callStatsConfIDNamespace - (optional) a namespace to prepend the callstats conference ID with. Defaults to the window.location.hostname
+    2. desktopSharingChromeExtId - The ID of the jidesha extension for Chrome. Example: 'mbocklcggfhnbahlnepmldehdhpjfcjp'
+    3. desktopSharingChromeDisabled - Boolean. Whether desktop sharing should be disabled on Chrome. Example: false.
+    4. desktopSharingChromeSources - Array of strings with the media sources to use when using screen sharing with the Chrome extension. Example: ['screen', 'window']
+    5. desktopSharingChromeMinExtVersion - Required version of Chrome extension. Example: '0.1'
+    6. desktopSharingFirefoxExtId - The ID of the jidesha extension for Firefox. If null, we assume that no extension is required.
+    7. desktopSharingFirefoxDisabled - Boolean. Whether desktop sharing should be disabled on Firefox. Example: false.
+    8. desktopSharingFirefoxMaxVersionExtRequired - The maximum version of Firefox which requires a jidesha extension. Example: if set to 41, we will require the extension for Firefox versions up to and including 41. On Firefox 42 and higher, we will run without the extension. If set to -1, an extension will be required for all versions of Firefox.
+    9. desktopSharingFirefoxExtensionURL - The URL to the Firefox extension for desktop sharing. "null" if no extension is required.
+    10. disableAudioLevels - boolean property. Enables/disables audio levels.
+    11. disableSimulcast - boolean property. Enables/disables simulcast.
+    12. enableWindowOnErrorHandler - boolean property (default false). Enables/disables attaching global onerror handler (window.onerror).
+    13. disableThirdPartyRequests - if true - callstats will be disabled and the callstats API won't be included.
+    14. enableAnalyticsLogging - boolean property (default false). Enables/disables analytics logging.
+    15. callStatsCustomScriptUrl - (optional) custom url to access callstats client script
+    16. callStatsConfIDNamespace - (optional) a namespace to prepend the callstats conference ID with. Defaults to the window.location.hostname
 
 * ```JitsiMeetJS.JitsiConnection``` - the ```JitsiConnection``` constructor. You can use that to create new server connection.
 

doc/example/example.js

 // JitsiMeetJS.setLogLevel(JitsiMeetJS.logLevels.ERROR);
 var initOptions = {
     disableAudioLevels: true,
-    // Desktop sharing method. Can be set to 'ext', 'webrtc' or false to disable.
-    desktopSharingChromeMethod: 'ext',
     // The ID of the jidesha extension for Chrome.
     desktopSharingChromeExtId: 'mbocklcggfhnbahlnepmldehdhpjfcjp',
+    // Whether desktop sharing should be disabled on Chrome.
+    desktopSharingChromeDisabled: false,
     // The media sources to use when using screen sharing with the Chrome
     // extension.
     desktopSharingChromeSources: ['screen', 'window'],

modules/RTC/ScreenObtainer.js

      * Initializes the function used to obtain a screen capture
      * (this.obtainStream).
      *
-     * If the browser is Chrome, it uses the value of
-     * 'options.desktopSharingChromeMethod' (or 'options.desktopSharing') to
-     * decide whether to use the a Chrome extension (if the value is 'ext'),
-     * use the "screen" media source (if the value is 'webrtc'),
-     * or disable screen capture (if the value is other).
-     * Note that for the "screen" media source to work the
-     * 'chrome://flags/#enable-usermedia-screen-capture' flag must be set.
      * @param options {object}
      * @param gum {Function} GUM method
      */
         if (RTCBrowserType.isFirefox())
             initFirefoxExtensionDetection(options);
 
-        // TODO remove this, options.desktopSharing is deprecated.
-        var chromeMethod =
-            (options.desktopSharingChromeMethod || options.desktopSharing);
-
         if (RTCBrowserType.isNWJS()) {
             obtainDesktopStream = (options, onSuccess, onFailure) => {
                 window.JitsiMeetNW.obtainDesktopStream (
                 logger.info("Using Temasys plugin for desktop sharing");
             }
         } else if (RTCBrowserType.isChrome()) {
-            if (chromeMethod == "ext") {
-                if (RTCBrowserType.getChromeVersion() >= 34) {
-                    obtainDesktopStream =
-                        this.obtainScreenFromExtension;
-                    logger.info("Using Chrome extension for desktop sharing");
-                    initChromeExtension(options);
-                } else {
-                    logger.info("Chrome extension not supported until ver 34");
-                }
-            } else if (chromeMethod == "webrtc") {
-                obtainDesktopStream = obtainWebRTCScreen;
-                logger.info("Using Chrome WebRTC for desktop sharing");
+            if (options.desktopSharingChromeDisabled ||
+                options.desktopSharingChromeMethod === false ||
+                !options.desktopSharingChromeExtId) {
+                // TODO: desktopSharingChromeMethod is deprecated, remove.
+                obtainDesktopStream = null;
+            } else if (RTCBrowserType.getChromeVersion() >= 34) {
+                obtainDesktopStream =
+                    this.obtainScreenFromExtension;
+                logger.info("Using Chrome extension for desktop sharing");
+                initChromeExtension(options);
+            } else {
+                logger.info("Chrome extension not supported until ver 34");
             }
         } else if (RTCBrowserType.isFirefox()) {
             if (options.desktopSharingFirefoxDisabled) {
 /**
  * Constructs inline install URL for Chrome desktop streaming extension.
  * The 'chromeExtensionId' must be defined in options parameter.
- * @param options supports "desktopSharingChromeExtId" and "chromeExtensionId"
+ * @param options supports "desktopSharingChromeExtId"
  * @returns {string}
  */
 function getWebStoreInstallUrl(options)
 {
-    //TODO remove chromeExtensionId (deprecated)
     return "https://chrome.google.com/webstore/detail/" +
-        (options.desktopSharingChromeExtId || options.chromeExtensionId);
+        options.desktopSharingChromeExtId;
 }
 
 /**
         return;
     }
     chrome.runtime.sendMessage(
-        //TODO: remove chromeExtensionId (deprecated)
-        (options.desktopSharingChromeExtId || options.chromeExtensionId),
+        options.desktopSharingChromeExtId,
         { getVersion: true },
         response => {
             if (!response || !response.version) {
             // Check installed extension version
             var extVersion = response.version;
             logger.log('Extension version is: ' + extVersion);
-            //TODO: remove minChromeExtVersion (deprecated)
             var updateRequired
                 = isUpdateRequired(
-                    (options.desktopSharingChromeMinExtVersion ||
-                        options.minChromeExtVersion),
+                    options.desktopSharingChromeMinExtVersion,
                     extVersion);
             callback(!updateRequired, updateRequired);
         }
     // Sends 'getStream' msg to the extension.
     // Extension id must be defined in the config.
     chrome.runtime.sendMessage(
-        //TODO: remove chromeExtensionId (deprecated)
-        (options.desktopSharingChromeExtId || options.chromeExtensionId),
+        options.desktopSharingChromeExtId,
         {
             getStream: true,
-            //TODO: remove desktopSharingSources (deprecated).
-            sources: (options.desktopSharingChromeSources ||
-                options.desktopSharingSources)
+            sources: options.desktopSharingChromeSources
         },
         response => {
             if (!response) {
  * Initializes <link rel=chrome-webstore-item /> with extension id set in
  * config.js to support inline installs. Host site must be selected as main
  * website of published extension.
- * @param options supports "desktopSharingChromeExtId" and "chromeExtensionId"
+ * @param options supports "desktopSharingChromeExtId"
  */
 function initInlineInstalls(options)
 {
 /**
  * Starts the detection of an installed jidesha extension for firefox.
  * @param options supports "desktopSharingFirefoxDisabled",
- * "desktopSharingFirefoxExtId" and "chromeExtensionId"
+ * "desktopSharingFirefoxExtId"
  */
 function initFirefoxExtensionDetection(options) {
     if (options.desktopSharingFirefoxDisabled) {