Publish Escalator.getBodyRowCount to JS (#20344)

This is needed to be able to get the information from e.g. TestBench

Change-Id: I95ec6064f602e6a8b24e35cc59d467e9c8b31c1e

client/src/main/java/com/vaadin/client/widgets/Escalator.java

         /*-{
             var vScroll = esc.@com.vaadin.client.widgets.Escalator::verticalScrollbar;
             var vScrollElem = vScroll.@com.vaadin.client.widget.escalator.ScrollbarBundle::getElement()();
-        
+
             var hScroll = esc.@com.vaadin.client.widgets.Escalator::horizontalScrollbar;
             var hScrollElem = hScroll.@com.vaadin.client.widget.escalator.ScrollbarBundle::getElement()();
-        
+
             return $entry(function(e) {
                 var target = e.target;
-        
+
                 // in case the scroll event was native (i.e. scrollbars were dragged, or
                 // the scrollTop/Left was manually modified), the bundles have old cache
                 // values. We need to make sure that the caches are kept up to date.
             return $entry(function(e) {
                 var deltaX = e.deltaX ? e.deltaX : -0.5*e.wheelDeltaX;
                 var deltaY = e.deltaY ? e.deltaY : -0.5*e.wheelDeltaY;
-        
+
                 // Delta mode 0 is in pixels; we don't need to do anything...
-        
+
                 // A delta mode of 1 means we're scrolling by lines instead of pixels
                 // We need to scale the number of lines by the default line height
                 if(e.deltaMode === 1) {
                     var brc = esc.@com.vaadin.client.widgets.Escalator::body;
                     deltaY *= brc.@com.vaadin.client.widgets.Escalator.AbstractRowContainer::getDefaultRowHeight()();
                 }
-        
+
                 // Other delta modes aren't supported
                 if((e.deltaMode !== undefined) && (e.deltaMode >= 2 || e.deltaMode < 0)) {
                     var msg = "Unsupported wheel delta mode \"" + e.deltaMode + "\"";
-        
+
                     // Print warning message
                     esc.@com.vaadin.client.widgets.Escalator::logWarning(*)(msg);
                 }
-        
+
                 // IE8 has only delta y
                 if (isNaN(deltaY)) {
                     deltaY = -0.5*e.wheelDelta;
                 }
-        
+
                 @com.vaadin.client.widgets.Escalator.JsniUtil::moveScrollFromEvent(*)(esc, deltaX, deltaY, e);
             });
         }-*/;
         // init default dimensions
         setHeight(null);
         setWidth(null);
+
+        publishJSHelpers(root);
+    }
+
+    private int getBodyRowCount() {
+        return getBody().getRowCount();
     }
 
+    private native void publishJSHelpers(Element root)
+    /*-{
+        var self = this;
+        root.getBodyRowCount = $entry(function () {
+           return self.@Escalator::getBodyRowCount()();
+        });
+    }-*/;
+
     private void setupScrollbars(final Element root) {
 
         ScrollHandler scrollHandler = new ScrollHandler() {

uitest/src/test/java/com/vaadin/v7/tests/components/grid/basicfeatures/server/GridStructureTest.java

         selectMenuPath("Component", "Body rows", "Add third row");
         assertFalse(logContainsText("Exception occured"));
     }
+
+    @Test
+    public void getBodyRowCountJS() {
+        openTestURL();
+        GridElement grid = $(GridElement.class).first();
+        assertEquals(1000L,
+                executeScript("return arguments[0].getBodyRowCount()", grid));
+        selectMenuPath("Component", "Body rows", "Remove all rows");
+        assertEquals(0L,
+                executeScript("return arguments[0].getBodyRowCount()", grid));
+        selectMenuPath("Component", "Body rows", "Add first row");
+        assertEquals(1L,
+                executeScript("return arguments[0].getBodyRowCount()", grid));
+    }
 }