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
if (PreferenceConstants.EDITOR_SYNC_OUTLINE_ON_CURSOR_MOVE.equals(property)) {
				if (newBooleanValue)
					selectionChanged();
				return;
			}
			
			if (PreferenceConstants.EDITOR_MARK_OCCURRENCES.equals(property)) {
				if (newBooleanValue != fMarkOccurrenceAnnotations) {
					fMarkOccurrenceAnnotations= newBooleanValue;
					if (!fMarkOccurrenceAnnotations)
						uninstallOccurrencesFinder();
					else
						installOccurrencesFinder();
				}
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_TYPE_OCCURRENCES.equals(property)) {
				fMarkTypeOccurrences= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_METHOD_OCCURRENCES.equals(property)) {
				fMarkMethodOccurrences= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_CONSTANT_OCCURRENCES.equals(property)) {
				fMarkConstantOccurrences= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_FIELD_OCCURRENCES.equals(property)) {