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
return false;
		}
		
		/**
		 * Add a position with the given range and highlighting iff it does not exist already.
		 * @param offset The range offset
		 * @param length The range length
		 * @param highlighting The highlighting
		 */
		private void addPosition(int offset, int length, Highlighting highlighting) {
			boolean isExisting= false;
			
			for (int i= 0, n= fRemovedPositions.size(); i < n; i++) {
				HighlightedPosition position= (HighlightedPosition) fRemovedPositions.get(i);
				if (position == null)
					continue;
				if (position.isEqual(offset, length, highlighting)) {
					isExisting= true;
					fRemovedPositions.set(i, null);
					fNOfRemovedPositions--;
					break;
				}
			}
			if (!isExisting) {
				Position position= fJobPresenter.createHighlightedPosition(offset, length, highlighting);
				fAddedPositions.add(position);
			}
		}
		/**
		 * Retain the positions completely contained in the given range.