Bug 93360 [Viewers] getChild still used in indexForElement
indexForElement() in AbstractTreeViewer still uses getChild() and not getChildren(). This should probably also change to using getChildren() and do the same thing as insertionPosition().
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
return size;
	    int min = lastInsertion, max = size - 1;
		while (min <= max) {
            int mid = (min + max) / 2;
            Object data = items[mid].getData();
            int compare = sorter.compare(this, data, element);
            if (compare == 0) {
                
                while (compare == 0) {
                    ++mid;
                    if (mid >= size) {
                        break;
                    }
                    data = items[mid].getData();
                    compare = sorter.compare(this, data, element);
                }
                return mid;
            }
            if (compare < 0)
                min = mid + 1;
            else
                max = mid - 1;
	        }
	   return min;
	    
			
	}
	/**
     * Returns the index where the item should be inserted. It uses sorter to
     * determine the correct position, if sorter is not assigned, returns the