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
fPresenter= presenter;
		fSemanticHighlightings= semanticHighlightings;
		fHighlightings= highlightings;
		
		fEditor= editor;
		fSourceViewer= sourceViewer;
		
		if (fEditor instanceof CompilationUnitEditor)
			((CompilationUnitEditor)fEditor).addReconcileListener(this);
		else {
			fSourceViewer.addTextInputListener(this);
			scheduleJob();
		}
	}
	
	/**
	 * Uninstall this reconciler from the editor
	 */
	public void uninstall() {
		if (fPresenter != null)
			fPresenter.setCanceled(true);
		
		if (fEditor != null) {
			if (fEditor instanceof CompilationUnitEditor)
				((CompilationUnitEditor)fEditor).removeReconcileListener(this);
			else
				fSourceViewer.removeTextInputListener(this);
			fEditor= null;
		}