Bug 211212 Cannot delete a bookmark in the new markers view
The delete action is not enabled for bookmarks
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/EditablePropertyTester.java
private static final Object EDITABLE = "editable"; 
	/**
	 * Create a new instance of the receiver.
	 */
	public EditablePropertyTester() {
		super();
	}
	/* (non-Javadoc)
	 * @see org.eclipse.core.expressions.IPropertyTester#test(java.lang.Object, java.lang.String, java.lang.Object[], java.lang.Object)
	 */
	public boolean test(Object receiver, String property, Object[] args,
			Object expectedValue) {
		if (property.equals(EDITABLE)) {
			IMarker marker = ((MarkerEntry) receiver).getMarker();
			if (marker != null)
				return marker.getAttribute(IMarker.USER_EDITABLE, false);
		}
		return false;
	}
}