Bug 96917 [implementation] If two editors use the 2.x-compatible API, one or both doesn't work
At least one problem is that 3.0 installs partitioners for every editor that might possibly edit a file, but each editor expects its own partitioner to be installed. Leading to the famous white screen with blue line.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/ClassFileDocumentProvider.java
}
	/**
	 * Handles the deletion of the element underlying the given class file editor input.
	 * @param input the editor input
	 */
	protected void handleDeleted(IClassFileEditorInput input) {
		fireElementDeleted(input);
	}
	/**
	 * Fires input changes to input change listeners.
	 */
	protected void fireInputChanged(IClassFileEditorInput input) {
		List list= new ArrayList(fInputListeners);
		for (Iterator i = list.iterator(); i.hasNext();)
			((InputChangeListener) i.next()).inputChanged(input);
	}
	/**
	 * Adds an input change listener.
	 */
	public void addInputChangeListener(InputChangeListener listener) {
		fInputListeners.add(listener);
	}
	/**
	 * Removes an input change listener.
	 */
	public void removeInputChangeListener(InputChangeListener listener) {
		fInputListeners.remove(listener);
	}
}