Bug 75711 AstProvider should not create AST if requested by SelectionListenerWithASTManager
3.1 M2 If SelectionListenerWithASTManager waits for an AST and the editor closes we should not create an AST for that one but return null instead.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
/*
		 * @see org.eclipse.swt.events.ShellAdapter#shellActivated(org.eclipse.swt.events.ShellEvent)
		 */
		public void shellActivated(ShellEvent e) {
			if (fMarkOccurrenceAnnotations && isActivePart()) {
				fForcedMarkOccurrencesSelection= getSelectionProvider().getSelection();
				SelectionListenerWithASTManager.getDefault().forceSelectionChange(JavaEditor.this, (ITextSelection)fForcedMarkOccurrencesSelection);
			}
		}
		
		/*
		 * @see org.eclipse.swt.events.ShellAdapter#shellDeactivated(org.eclipse.swt.events.ShellEvent)
		 */
		public void shellDeactivated(ShellEvent e) {
			removeOccurrenceAnnotations();
		}
	}
	
	protected final static String LINK_COLOR= PreferenceConstants.EDITOR_LINK_COLOR;
	
	protected final static String MATCHING_BRACKETS=  PreferenceConstants.EDITOR_MATCHING_BRACKETS;
	
	protected final static String MATCHING_BRACKETS_COLOR=  PreferenceConstants.EDITOR_MATCHING_BRACKETS_COLOR;