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
/**
	 * An input change listener to request the editor to reread the input.
	 */
	public interface InputChangeListener {
		void inputChanged(IClassFileEditorInput input);
	}
	/**
	 * Synchronizes the document with external resource changes.
	 */
	protected class ClassFileSynchronizer implements IElementChangedListener {
		protected IClassFileEditorInput fInput;
		protected IPackageFragmentRoot fPackageFragmentRoot;
		/**
		 * Default constructor.
		 */
		public ClassFileSynchronizer(IClassFileEditorInput input) {
			fInput= input;
			IJavaElement parent= fInput.getClassFile().getParent();
			while (parent != null && !(parent instanceof IPackageFragmentRoot)) {
				parent= parent.getParent();
			}
			fPackageFragmentRoot= (IPackageFragmentRoot) parent;
		}
		/**
		 * Installs the synchronizer.
		 */
		public void install() {
			JavaCore.addElementChangedListener(this);
		}
		/**