Bug 25845 Support for manually attaching source to a class path container
From Dejan: There is a work item on the ability to manually attach source to classpath entries managed by classpath container. We discussed it and we have workable options but we would like if we can have it by M3 because we want to start self-hosting using classpath containers ourselves.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/ClassFileEditor.java
private final IClassFile fFile;
			private ScrolledComposite fScrolledComposite;
			private Color fBackgroundColor;
			private Color fForegroundColor;
			private Color fSeparatorColor;
			private List fBannerLabels= new ArrayList();
			private List fHeaderLabels= new ArrayList();
			private Font fFont;
			
			/**
			 * Creates a source attachment form for a class file. 
			 */
			public SourceAttachmentForm(IClassFile file) {
				fFile= file;
			}
		
			/**
			 * Returns the package fragment root of this file.
			 */
			private IPackageFragmentRoot getPackageFragmentRoot(IClassFile file) {
		
				IJavaElement element= file.getParent();
				while (element != null && element.getElementType() != IJavaElement.PACKAGE_FRAGMENT_ROOT)
					element= element.getParent();
		
				return (IPackageFragmentRoot) element;		
			}