Bug 30658 Package explorer drag'n drop does not always work
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
private boolean fIsCurrentLayoutFlat; 
	private static final int HIERARCHICAL_LAYOUT= 0x1;
	private static final int FLAT_LAYOUT= 0x2;
	
	public final static String VIEW_ID= JavaUI.ID_PACKAGES;
				
	
	static final String TAG_SELECTION= "selection"; 
	static final String TAG_EXPANDED= "expanded"; 
	static final String TAG_ELEMENT= "element"; 
	static final String TAG_PATH= "path"; 
	static final String TAG_VERTICAL_POSITION= "verticalPosition"; 
	static final String TAG_HORIZONTAL_POSITION= "horizontalPosition"; 
	static final String TAG_FILTERS = "filters"; 
	static final String TAG_FILTER = "filter"; 
	static final String TAG_LAYOUT= "layout"; 
	
	private PackageExplorerContentProvider fContentProvider;