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
/*
	 * @see AbstractTextEditor#handlePreferenceStoreChanged(PropertyChangeEvent)
	 */
	protected void handlePreferenceStoreChanged(PropertyChangeEvent event) {
		
		try {
			
			AdaptedSourceViewer asv= (AdaptedSourceViewer) getSourceViewer();
			if (asv != null) {
					
				String p= event.getProperty();		
				
				if (CLOSE_BRACKETS.equals(p)) {
					fBracketInserter.setCloseBracketsEnabled(getPreferenceStore().getBoolean(p));
					return;	
				}
				if (CLOSE_STRINGS.equals(p)) {
					fBracketInserter.setCloseStringsEnabled(getPreferenceStore().getBoolean(p));
					return;
				}
								
				if (SPACES_FOR_TABS.equals(p)) {
					if (isTabConversionEnabled())
						startTabConversion();
					else
						stopTabConversion();
					return;
				}
				IContentAssistant c= asv.getContentAssistant();
				if (c instanceof ContentAssistant)