Fix removing resize and drag curtains when window is closed (#10515)

Fixes #10514

client/src/main/java/com/vaadin/client/ui/VWindow.java

@@ -258,6 +258,12 @@ public class VWindow extends VOverlay implements ShortcutActionHandlerOwner,
                 .focusStoredElement();
 
         removeTabBlockHandlers();
+        // If you click while the window is being closed,
+        // a new dragging curtain might be added and will
+        // remain after detach. Theoretically a resize curtain can also remain
+        // if you manage to click on the resize element
+        hideDraggingCurtain();
+        hideResizingCurtain();
     }
 
     private void addTabBlockHandlers() {

uitest/src/main/java/com/vaadin/tests/components/window/CurtainRemainsOnModalWindowClose.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.tests.components.window;
+
+import com.vaadin.annotations.Widgetset;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUIWithLog;
+import com.vaadin.ui.Button;
+import com.vaadin.ui.Window;
+
+@Widgetset("com.vaadin.DefaultWidgetSet")
+public class CurtainRemainsOnModalWindowClose extends AbstractTestUIWithLog {
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        Window w = new Window(null,
+                new Button("try double or triple click here"));
+        w.addClickListener(e -> w.close());
+
+        Button open = new Button("open window");
+        open.addClickListener(e -> addWindow(w));
+        addComponent(open);
+
+    }
+
+}