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
return minLocation;
		}
	
		private Point getMaximumLocation(StyledText text, int offset, int length) {
			Point maxLocation= new Point(Integer.MIN_VALUE, Integer.MIN_VALUE);
	
			for (int i= 0; i <= length; i++) {
				Point location= text.getLocationAtOffset(offset + i);
				
				if (location.x > maxLocation.x)
					maxLocation.x= location.x;			
				if (location.y > maxLocation.y)
					maxLocation.y= location.y;			
			}	
			
			return maxLocation;
		}
	}
	
	/**
	 * Cancels the occurrences finder job upon document changes.
	 * 
	 * @since 3.0
	 */
	class OccurrencesFinderJobCanceler implements IDocumentListener, ITextInputListener {
		public void install() {
			ISourceViewer sourceViewer= getSourceViewer();
			if (sourceViewer == null)
				return;