Two new abstract methods is necessary to be added to 
xml.xam/src/org/netbeans/modules/xml/xam/AbstractComponent.java 
for the sake of performance enhancement

public void checkChildrenPopulated();
public void getChildrenCount();

Method getChildren() makes copy of children's list and it can be time consuming in case of big amount of children. 
The method is called very frequently in order to be sure that children are populated. But the output of the method 
isn't used at all. Another case is request of the children's count. In both cases it doesn't make sense to make
children's copy. So it's suggested to introduce two new methods. 

The AbstractComponent is an abstract implementation of the Component interface. I put the methods to the class but not
to the interface at first because the performance experiments proofed that it is sufficient. And also it should reduce
impact to backward compatibility. Though I'm quite sure AbstractComponent class is the only direct implementation of
Component interface.