Allow users to add third-party VPNs from the settings page

chrome/browser/resources/options/chromeos/vpn_providers.js

Index: chrome/browser/resources/options/chromeos/vpn_providers.js
diff --git a/chrome/browser/resources/options/chromeos/vpn_providers.js b/chrome/browser/resources/options/chromeos/vpn_providers.js
index 911c68487fbf67238d92644ad4eb93e2329bdd87..06da41b5339940a846dcf01029334353b6eca1f3 100644
--- a/chrome/browser/resources/options/chromeos/vpn_providers.js
+++ b/chrome/browser/resources/options/chromeos/vpn_providers.js
@@ -26,6 +26,34 @@ cr.define('options', function() {
     providers_: [],
 
     /**
+     * Observers who will be called when the list of VPN providers changes.
+     * @type {!Array<!function()>}
+     */
+    observers_: [],
+
+    /**
+     * The VPN providers enabled in the primary user's profile.
+     * @type {!Array<{name: string, extensionID: ?string}>}
+     */
+    get providers() {
+      return this.providers_;
+    },
+    set providers(providers) {
+      this.providers_ = providers;
+      for (var i = 0; i < this.observers_.length; ++i)
+        this.observers_[i]();
+    },
+
+    /**
+     * Adds an observer to be called when the list of VPN providers changes.
+     * @param {!function()} observer The observer to add.
+     * @private
+     */
+    addObserver_: function(observer) {
+      this.observers_.push(observer);
+    },
+
+    /**
      * Formats a network name for display purposes. If the network belongs to
      * a third-party VPN provider, the provider name is added to the network
      * name.
@@ -50,12 +78,23 @@ cr.define('options', function() {
   };
 
   /**
+   * Adds an observer to be called when the list of VPN providers changes. Note
+   * that an observer may in turn call setProviders() but should be careful not
+   * to get stuck in an infinite loop as every change to the list of VPN
+   * providers will cause the observers to be called again.
+   * @param {!function()} observer The observer to add.
+   */
+  VPNProviders.addObserver = function(observer) {
+    VPNProviders.getInstance().addObserver_(observer);
+  };
+
+  /**
    * Returns the list of VPN providers enabled in the primary user's profile.
    * @return {!Array<{name: string, extensionID: ?string}>} The list of VPN
    *     providers enabled in the primary user's profile.
    */
   VPNProviders.getProviders = function() {
-    return VPNProviders.getInstance().providers_;
+    return VPNProviders.getInstance().providers;
   };
 
   /**
@@ -64,7 +103,7 @@ cr.define('options', function() {
    *     of VPN providers enabled in the primary user's profile.
    */
   VPNProviders.setProviders = function(providers) {
-    VPNProviders.getInstance().providers_ = providers;
+    VPNProviders.getInstance().providers = providers;
   };
 
   /**