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
fMarkFieldOccurrences= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_LOCAL_VARIABLE_OCCURRENCES.equals(property)) {
				fMarkLocalVariableypeOccurrences= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_EXCEPTION_OCCURRENCES.equals(property)) {
				fMarkExceptions= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_METHOD_EXIT_POINTS.equals(property)) {
				fMarkMethodExitPoints= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_MARK_IMPLEMENTORS.equals(property)) {
				fMarkImplementors= newBooleanValue;
				return;
			}
			if (PreferenceConstants.EDITOR_STICKY_OCCURRENCES.equals(property)) {
				fStickyOccurrenceAnnotations= newBooleanValue;
				return;
			}
			if (SemanticHighlightings.affectsEnablement(getPreferenceStore(), event)) {
				if (isSemanticHighlightingEnabled())
					installSemanticHighlighting();
				else
					uninstallSemanticHighlighting();
				return;
			}