Bug 204935 [Markers] MarkersView should use fixed default widths
The MarkersView should use fixed rather than proportional widths as columns are getting very small when the workbench is restarted with a small markers view.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/ExtendedMarkersView.java
* @return Clipboard
	 */
	Clipboard getClipboard() {
		if (clipboard == null)
			clipboard = new Clipboard(viewer.getControl().getDisplay());
		return clipboard;
	}
	/**
	 * Return the content provider for the receiver.
	 * 
	 * @return ILazyTreeContentProvider
	 */
	private ILazyTreeContentProvider getContentProvider(final TreeViewer viewer) {
		return new ILazyTreeContentProvider() {
			/*
			 * (non-Javadoc)
			 * 
			 * @see org.eclipse.jface.viewers.IContentProvider#dispose()
			 */
			public void dispose() {
			}
			/*
			 * (non-Javadoc)
			 * 
			 * @see org.eclipse.jface.viewers.ILazyTreeContentProvider#getParent(java.lang.Object)
			 */
			public Object getParent(Object element) {
				Object parent = ((MarkerItem) element).getParent();
				if (parent == null)
					return builder;