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/SemanticHighlightingReconciler.java
private SemanticToken fToken= new SemanticToken();
		
		/*
		 * @see org.eclipse.jdt.internal.corext.dom.GenericVisitor#visitNode(org.eclipse.jdt.core.dom.ASTNode)
		 */
		protected boolean visitNode(ASTNode node) {
			if ((node.getFlags() & ASTNode.MALFORMED) == ASTNode.MALFORMED) {
				retainPositions(node.getStartPosition(), node.getLength());
				return false; 
			}
			return true;
		}
		
		/*
		 * @see org.eclipse.jdt.core.dom.ASTVisitor#visit(org.eclipse.jdt.core.dom.SimpleName)
		 */
		public boolean visit(SimpleName node) {
			fToken.update(node);
			for (int i= 0, n= fJobSemanticHighlightings.length; i < n; i++) {
				SemanticHighlighting semanticHighlighting= fJobSemanticHighlightings[i];
				if (fJobHighlightings[i].isEnabled() && semanticHighlighting.consumes(fToken)) {
					addPosition(node.getStartPosition(), node.getLength(), fJobHighlightings[i]);
					break;
				}
			}
			fToken.clear();