Guard clipping to avoid resize artifacts in tree viewer

 Setting the clipping region temporarily to the textBounds   was originally added (https://bugs.eclipse.org/bugs/show_bug.cgi?id=291245 comment 25) to prevent images
 from being overdrawn when implementting  RIGHT or CENTER column alignment support in StyledCellLabelProvider. However, enabling
 clipping causes artifact lines during tree resizing, as a temporary workaround the  clipping call is
 now guarded and applied only in those alignment cases to avoid issues with resizing of columns.

Author: arunjose696

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

@@ -389,7 +389,7 @@ protected void paint(Event event, Object element) {
 			int y = textBounds.y
 					+ Math.max(0, (textBounds.height - layoutBounds.height) / 2);
 
-			if (gc.isClipped()) {
+			if (gc.isClipped() && ((style & SWT.RIGHT) != 0 || (style & SWT.CENTER) != 0)) {
 				Rectangle saveClipping = gc.getClipping();
 				gc.setClipping(textBounds);
 				textLayout.draw(gc, x, y);