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
return false;
		
		int kind= binding.getKind();
		if (fMarkTypeOccurrences && kind == IBinding.TYPE)
			return true;
		if (fMarkMethodOccurrences && kind == IBinding.METHOD)
			return true;
		if (kind == IBinding.VARIABLE) {
			IVariableBinding variableBinding= (IVariableBinding)binding;
			if (variableBinding.isField()) {
				int constantModifier= IModifierConstants.ACC_STATIC | IModifierConstants.ACC_FINAL;
				boolean isConstant= (variableBinding.getModifiers() & constantModifier) == constantModifier; 
				if (isConstant)
					return fMarkConstantOccurrences;
				else
					return fMarkFieldOccurrences;
			}
			
			return fMarkLocalVariableypeOccurrences;
		}
		return false;
	}
	
	void removeOccurrenceAnnotations() {
		IDocumentProvider documentProvider= getDocumentProvider();
		if (documentProvider == null)
			return;
		
		IAnnotationModel annotationModel= documentProvider.getAnnotationModel(getEditorInput());
		if (annotationModel == null || fOccurrenceAnnotations == null)