[extensions-web] Assume that API methods may return deferred object.

[Olav Vitters <ovitters src gnome org>]

commit b576313701842acf00465e92d181b05d36a0832c
Author: Yuri Konotopov <ykonotopov gmail com>
Date:   Wed Jan 6 22:40:48 2016 +0300

    Assume that API methods may return deferred object.
    
    Fixes: https://bugzilla.gnome.org/show_bug.cgi?id=760225

 sweettooth/static/js/versions/common/common.js |   32 ++++++++++++++++++++---
 1 files changed, 27 insertions(+), 5 deletions(-)
---
diff --git a/sweettooth/static/js/versions/common/common.js b/sweettooth/static/js/versions/common/common.js
index db7faca..6ae9bc4 100644
--- a/sweettooth/static/js/versions/common/common.js
+++ b/sweettooth/static/js/versions/common/common.js
@@ -4,15 +4,25 @@ define(['jquery', 'dbus!API'], function($, API) {
     "use strict";
 
     function _makeRawPromise(result) {
-        // Make a new completed promise -- when we move the plugin
-        // over to async, we can remove this.
+        // Check if result is promise already
+        if(isPromise(result))
+            return result;
+
         return (new $.Deferred()).resolve(result);
     }
 
     function _makePromise(result) {
+        // Check if result is promise already
+        if(isPromise(result))
+            return result;
+
         return _makeRawPromise(JSON.parse(result));
     }
 
+    function isPromise(value) {
+        return value && value.promise;
+    }
+
     return {
         _makePromise: _makePromise,
 
@@ -43,18 +53,30 @@ define(['jquery', 'dbus!API'], function($, API) {
         },
 
         InstallExtensionOne: function(uuid) {
-            API.installExtension(uuid);
+            var result = API.installExtension(uuid);
+
+            if(isPromise(result))
+                   return result;
+
             return _makeRawPromise('succeeded');
         },
 
         InstallExtensionTwo: function(uuid) {
-            API.installExtension(uuid, "");
+            var result = API.installExtension(uuid, "");
+
+            if(isPromise(result))
+                   return result;
+
             return _makeRawPromise('succeeded');
         },
 
         InstallExtensionAsync: function(uuid) {
             var d = new $.Deferred();
-            API.installExtension(uuid, d.done.bind(d), d.fail.bind(d));
+            var result = API.installExtension(uuid, d.done.bind(d), d.fail.bind(d));
+
+            if(isPromise(result))
+                   return result;
+
             return d;
         },