Also remove SWT.BACKGROUND when handling SWT.EraseItem

Removing the bit is necessary so that Linux and Mac do not overwrite the
background color later. This was noticed by @Christopher-Hermann during
a review and the problem showed up in the AST view.

Author: fedejeanne

bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerSelectionColorListener.java

@@ -196,8 +196,10 @@ private void handleEraseItem(Event event) {
 		int rowWidth = (event.widget instanceof Scrollable s) ? s.getClientArea().width : event.width;
 		gc.fillRectangle(0, event.y, rowWidth, event.height);
 
-		// Prevent native selection drawing
-		event.detail &= ~SWT.SELECTED;
+		// Remove SELECTED and BACKGROUND flags to prevent native drawing from
+		// overwriting our custom colors. Removing SWT.BACKGROUND is necessary for Linux
+		// and Mac (Windows works just fine even when the bit has not been removed
+		event.detail &= ~(SWT.SELECTED & SWT.BACKGROUND);
 	}
 
 	private void handlePaintItem(Event event) {