Bug 81983 [preferences] Disabling and enabling folding on small file takes forever
3.1 M4 Using enable/disable folding on a small CU takes forever. This is caused by the recent change to apply the preference to all Java editors. In another (hidden) window (Debug) I had StyledText open which (understandably) took long to react on the preference change. Non-visible editor's should not react to this change until they become visible.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
fOutlineSelectionChangedListener.install(fOutlinePage);
		}
	}
		
	/**
	 * Synchronizes the outliner selection with the actual cursor
	 * position in the editor.
	 */
	public void synchronizeOutlinePageSelection() {
		synchronizeOutlinePage(computeHighlightRangeSourceReference());
	}
	
	
	/*
	 * Get the desktop's StatusLineManager
	 */
	protected IStatusLineManager getStatusLineManager() {
		IEditorActionBarContributor contributor= getEditorSite().getActionBarContributor();
		if (contributor instanceof EditorActionBarContributor) {
			return ((EditorActionBarContributor) contributor).getActionBars().getStatusLineManager();
		}
		return null;
	}	
	
	/*
	 * @see AbstractTextEditor#getAdapter(Class)
	 */
	public Object getAdapter(Class required) {
		
		if (IContentOutlinePage.class.equals(required)) {