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
* @see org.eclipse.ui.texteditor.AbstractTextEditor#isEditable()
	 */
	public boolean isEditable() {
		return false;
	}
	
	/**
	 * Translates the given editor input into an <code>ExternalClassFileEditorInput</code>
	 * if it is a file editor input representing an external class file.
	 * 
	 * @param input the editor input to be transformed if necessary
	 * @return the transformed editor input
	 */
	protected IEditorInput transformEditorInput(IEditorInput input) {
		
		if (input instanceof IFileEditorInput) {
			IFile file= ((IFileEditorInput) input).getFile();
			IClassFileEditorInput classFileInput= new ExternalClassFileEditorInput(file);
			if (classFileInput.getClassFile() != null)
				input= classFileInput;
		}
		
		return input;
	}
	
	/*
	 * @see AbstractTextEditor#doSetInput(IEditorInput)
	 */
	protected void doSetInput(IEditorInput input) throws CoreException {
		input= transformEditorInput(input);