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
/**
		 * Creates a new smart line start action
		 * 
		 * @param textWidget the styled text widget
		 * @param doSelect a boolean flag which tells if the text up to the beginning of the line should be selected
		 */
		public SmartLineStartAction(final StyledText textWidget, final boolean doSelect) {
			super(textWidget, doSelect);
		}
		/*
		 * @see org.eclipse.ui.texteditor.AbstractTextEditor.LineStartAction#getLineStartPosition(java.lang.String, int, java.lang.String)
		 */
		protected int getLineStartPosition(final IDocument document, final String line, final int length, final int offset) {
			String type= IDocument.DEFAULT_CONTENT_TYPE;