Bug 157174 [Viewers] Refactor new Viewer API
We are yet not completely happy with the API and refactor it.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TableViewer.java
Assert.isTrue(!(getContentProvider() instanceof ILazyContentProvider),
				"Cannot get raw children with an ILazyContentProvider");
		return super.getRawChildren(parent);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.StructuredViewer#assertContentProviderType(org.eclipse.jface.viewers.IContentProvider)
	 */
	protected void assertContentProviderType(IContentProvider provider) {
		Assert.isTrue(provider instanceof IStructuredContentProvider
				|| provider instanceof ILazyContentProvider);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.StructuredViewer#getRowPartFromItem(org.eclipse.swt.widgets.Widget)
	 */
	protected ViewerRow getRowPartFromItem(Widget item) {
		ViewerRow part = (ViewerRow) item.getData(ViewerRow.ROWPART_KEY);
		if (part == null) {
			part = new TableViewerRow(((TableItem) item));
		}
		return part;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.StructuredViewer#createNewRowPart(org.eclipse.jface.internal.viewers.RowPart,
	 *      int, int)