Bug 40772 [plan item] Smart tab on empty lines
When having the caret on an empty line, pressing tab cleans up the line and sets the caret it the right indentation column.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
fBracketLevelStack.push(level);
					
					level.fManager= new LinkedPositionManager(document, fBracketLevelStack.size() > 1);
					level.fManager.addPosition(offset + 1, 0);
					level.fOffset= offset;
					level.fLength= 2;
			
					level.fEditor= new LinkedPositionUI(sourceViewer, level.fManager);
					level.fEditor.setCancelListener(this);
					level.fEditor.setExitPolicy(new ExitPolicy(closingCharacter, getEscapeCharacter(closingCharacter), fBracketLevelStack));
					level.fEditor.setFinalCaretOffset(offset + 2);
					level.fEditor.enter();
					
					
					IRegion newSelection= level.fEditor.getSelectedRegion();
					sourceViewer.setSelectedRange(newSelection.getOffset(), newSelection.getLength());
	
					event.doit= false;
				} catch (BadLocationException e) {
				}
				break;	
			}
		}
		
		/*
		 * @see org.eclipse.jdt.internal.ui.text.link.LinkedPositionUI.ExitListener#exit(boolean)
		 */
		public void exit(boolean accept) {
			
			BracketLevel level= (BracketLevel) fBracketLevelStack.pop();