Added HostListApl implementation to connect to legacy directory and GCD.

remoting/webapp/crd/js/host_list_api.js

Index: remoting/webapp/crd/js/host_list_api.js
diff --git a/remoting/webapp/crd/js/host_list_api.js b/remoting/webapp/crd/js/host_list_api.js
index 421314e855065e4c08040f9a65af095210fa3de4..65d08b66e21822530494f30d49096ccfe2e7bd7c 100644
--- a/remoting/webapp/crd/js/host_list_api.js
+++ b/remoting/webapp/crd/js/host_list_api.js
@@ -71,6 +71,15 @@ remoting.HostListApi.prototype.getSupportHost = function(supportId) {
 };
 
 /**
+ * Get the host ID from the contents of a host config file.
+ *
+ * @param {!Object} config
+ * @return {string}
+ */
+remoting.HostListApi.prototype.getHostIdFromConfig = function(config) {
+};
+
+/**
  * @private {remoting.HostListApi}
  */
 var instance = null;
@@ -80,9 +89,13 @@ var instance = null;
  */
 remoting.HostListApi.getInstance = function() {
   if (instance == null) {
-    instance = remoting.settings.USE_GCD ?
-        new remoting.GcdHostListApi() :
-        new remoting.LegacyHostListApi();
+    if (remoting.settings.USE_GCD) {
+      var gcdInstance = new remoting.GcdHostListApi();
+      var legacyInstance = new remoting.LegacyHostListApi();
+      instance = new remoting.CombinedHostListApi(legacyInstance, gcdInstance);
+    } else {
+      instance = new remoting.LegacyHostListApi();
+    }
   }
   return instance;
 };