Bug 567360 - add css class definition instead overriding css id

Change-Id: Ic1d979e4ed1c29d3a365f39082b569744e4bdcea
Signed-off-by: Reto Urfer <reto.urfer@pop.agri.ch>
diff --git a/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/ToolBarManagerRenderer.java b/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/ToolBarManagerRenderer.java
index 22a67ba..73fb37f 100644
--- a/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/ToolBarManagerRenderer.java
+++ b/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/ToolBarManagerRenderer.java
@@ -42,6 +42,7 @@
 import org.eclipse.e4.core.di.annotations.Optional;
 import org.eclipse.e4.core.services.events.IEventBroker;
 import org.eclipse.e4.core.services.log.Logger;
+import org.eclipse.e4.ui.css.swt.dom.WidgetElement;
 import org.eclipse.e4.ui.di.UIEventTopic;
 import org.eclipse.e4.ui.internal.workbench.ContributionsAnalyzer;
 import org.eclipse.e4.ui.internal.workbench.OpaqueElementUtil;
@@ -400,7 +401,15 @@
 		// CSS engine to target it
 		IStylingEngine engine = getContextForParent(element).get(IStylingEngine.class);
 		if (engine != null) {
-			engine.setId(toolbarComposite, "ToolbarComposite");//$NON-NLS-1$
+			String cssClass = WidgetElement.getCSSClass(toolbarComposite);
+			if (cssClass != null && !cssClass.isEmpty()) {
+				if (!cssClass.contains("ToolbarComposite")) {//$NON-NLS-1$
+					cssClass = cssClass + " ToolbarComposite"; //$NON-NLS-1$
+				}
+			} else {
+				cssClass = "ToolbarComposite"; //$NON-NLS-1$
+			}
+			engine.setClassname(toolbarComposite, cssClass);
 		}
 
 		final MToolBar toolbarModel = (MToolBar) element;