Bug 327522 Several main menus gone
I20101007-1949. 1. start new workspace 2. paste this snippet into Package Explorer: "class A {}" 3. close the editor (doesn't matter if you save or not) ==> several main menus (e.g. 'Refactor') are gone. ==> selecting another element in the view does not bring it back Nothing in .log.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartActivationHistory.java
* Checks to see if this element and its parents are actually being rendered.
	 */
	private boolean isValid(MUIElement element) {
		if (element instanceof MApplication) {
			return true;
		}
		MElementContainer<MUIElement> parent = element.getParent();
		if (parent == null) {
			MPlaceholder placeholder = element.getCurSharedRef();
			if (placeholder == null) {
				return false;
			}
			parent = placeholder.getParent();
			if (parent == null) {
				return false;
			}
		}
		return element.isToBeRendered() && element.isVisible() && isValid(parent);
	}
	/**
	 * Determines whether this element is contained within an MArea, and to return the area if it
	 * is.
	 */
	private MArea isInArea(MUIElement element) {
		MPlaceholder placeholder = element.getCurSharedRef();
		MUIElement parent = placeholder == null ? element.getParent() : placeholder.getParent();
		return parent instanceof MApplication ? null : parent instanceof MArea ? (MArea) parent
				: isInArea(parent);
	}
	/**