Fix LineNumberRuler for fixed zoom

This commit adds a layout call to the callback executed after a zoom
change for the Canvas. If a fixed zoom is used and monitor specific
scaling is active the font sizes will be correctly adapted after a zoom
change, but the size of the Canvas is not, leading to cut off line
numbers. Forcing a layout for this rare case of event will ensure a
proper resizing.
contributes to #3061

Author: akoch-yatta

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/source/LineNumberRulerColumn.java

@@ -624,6 +624,7 @@ public void addMouseListener(MouseListener listener) {
 					fBuffer.dispose();
 					fBuffer= null;
 				}
+				layout(false);
 			});
 		});