Update ComboBox for new DataSource and communication mechanism

This simplifies the client side state machine.

This change does not modify the CSS class name v-filterselect.

Change-Id: I2f4a6e5252045cb7698d582be90693e00961b342

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

@@ -0,0 +1,75 @@
+/*
+ * 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.client.ui;
+
+import com.google.gwt.core.client.JavaScriptObject;
+import com.google.gwt.dom.client.Element;
+import com.google.gwt.user.client.Event;
+import com.google.gwt.user.client.ui.Widget;
+import com.vaadin.client.widgets.Escalator;
+
+/**
+ * A mousewheel handling class to get around the limits of
+ * {@link Event#ONMOUSEWHEEL}.
+ *
+ * For internal use only. May be removed or replaced in the future.
+ *
+ * @see Escalator.JsniWorkaround
+ */
+// FIXME remove the copy in v7 package
+abstract class JsniMousewheelHandler {
+
+    /**
+     * A JavaScript function that handles the mousewheel DOM event, and passes
+     * it on to Java code.
+     *
+     * @see #createMousewheelListenerFunction(Widget)
+     */
+    protected final JavaScriptObject mousewheelListenerFunction;
+
+    protected JsniMousewheelHandler(final Widget widget) {
+        mousewheelListenerFunction = createMousewheelListenerFunction(widget);
+    }
+
+    /**
+     * A method that constructs the JavaScript function that will be stored into
+     * {@link #mousewheelListenerFunction}.
+     *
+     * @param widget
+     *            a reference to the current instance of {@link Widget}
+     */
+    protected abstract JavaScriptObject createMousewheelListenerFunction(
+            Widget widget);
+
+    public native void attachMousewheelListener(Element element)
+    /*-{
+        if (element.addEventListener) {
+            // FireFox likes "wheel", while others use "mousewheel"
+            var eventName = 'onmousewheel' in element ? 'mousewheel' : 'wheel';
+            element.addEventListener(eventName, this.@com.vaadin.client.ui.JsniMousewheelHandler::mousewheelListenerFunction);
+        }
+    }-*/;
+
+    public native void detachMousewheelListener(Element element)
+    /*-{
+        if (element.addEventListener) {
+            // FireFox likes "wheel", while others use "mousewheel"
+            var eventName = element.onwheel===undefined?"mousewheel":"wheel";
+            element.removeEventListener(eventName, this.@com.vaadin.client.ui.JsniMousewheelHandler::mousewheelListenerFunction);
+        }
+    }-*/;
+
+}