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
private boolean fMarkConstantOccurrences;
	/**
	 * Tells whether to mark field occurrences in this editor.
	 * Only valid if {@link #fMarkOccurrenceAnnotations} is <code>true</code>.
	 * @since 3.0
	 */
	private boolean fMarkFieldOccurrences;
	/**
	 * Tells whether to mark local variable occurrences in this editor.
	 * Only valid if {@link #fMarkOccurrenceAnnotations} is <code>true</code>.
	 * @since 3.0
	 */
	private boolean fMarkLocalVariableypeOccurrences;
	/**
	 * Tells whether to mark exception occurrences in this editor.
	 * Only valid if {@link #fMarkOccurrenceAnnotations} is <code>true</code>.
	 * @since 3.0
	 */
	private boolean fMarkExceptions;
	/**
	 * Tells whether to mark method exits in this editor.
	 * Only valid if {@link #fMarkOccurrenceAnnotations} is <code>true</code>.
	 * @since 3.0
	 */
	private boolean fMarkMethodExitPoints;
	/**
	 * Tells whether to mark implementors in this editor.
	 * Only valid if {@link #fMarkOccurrenceAnnotations} is <code>true</code>.
	 * @since 3.1
	 */