Hide log by setting width/height to 0 so that the same spacing is used

as in Vaadin 6 (to ease screenshot migration)

WebContent/VAADIN/themes/base/common/common.css

@@ -239,4 +239,8 @@ div.v-app-loading {
     opacity: 0.5;
     filter: alpha(opacity=50);
     cursor: default;
+}
+
+.v-clip {
+	overflow: hidden;
 }

tests/testbench/com/vaadin/tests/components/AbstractComponentTest.java

@@ -157,11 +157,23 @@ public abstract class AbstractComponentTest<T extends AbstractComponent>
     }
 
     protected void setLogVisible(boolean visible) {
-        log.setVisible(visible);
+        // This is only to be screenshot-compatible with Vaadin 6, where
+        // invisible components cause spacing
+        if (visible) {
+            log.setHeight(null);
+            log.setWidth(null);
+            log.setCaption((String) log.getData());
+        } else {
+            log.setHeight("0px");
+            log.setWidth("0px");
+            log.setCaption(null);
+        }
     }
 
     private void createLog() {
         log = new Log(5).setNumberLogRows(true);
+        log.setData(log.getCaption());
+        log.setStyleName("v-clip");
         getLayout().addComponent(log, 1);
     }