Fix preview animation

package.json

@@ -109,7 +109,7 @@
         "c9.ide.run.build": "#0598fff697",
         "c9.ide.run.debug.xdebug": "#9956689819",
         "c9.ide.save": "#4cda35bfdb",
-        "c9.ide.scm": "#da84c63595",
+        "c9.ide.scm": "#770f11a3ad",
         "c9.ide.terminal.monitor": "#1a4092ede2",
         "c9.ide.test": "#102942ae4e",
         "c9.ide.test.mocha": "#fc053b23d2",

plugins/c9.ide.editors/tab.js

@@ -291,9 +291,9 @@ define(function(require, module, exports) {
                 load();
             });
             
-            plugin.on("beforeUnload", function(){
+            plugin.on("beforeUnload", function(e){
                 if (!plugin.meta.$closing) {
-                    if (close())
+                    if (close(e && e.animate === false))
                         return false;
                 }
             });

plugins/c9.ide.editors/tabmanager.js

@@ -1283,7 +1283,7 @@ define(function(require, module, exports) {
                 
                 // Or keep tab until the new one is loaded
                 else {
-                    previewTab.unload();
+                    previewTab.unload({ animate: false });
                 }
             }