Bug 51653 [navigation] Quick Outline: Should also show interface members
I200402102000 We should consider showing the inherited members for interfaces at least when the target type is an interface itself.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/JavaOutlineInformationControl.java
Item i= (Item) node;
				if (i.getData() instanceof IJavaElement) {
					IJavaElement je= (IJavaElement) i.getData();
					if (je.getElementType() == IJavaElement.IMPORT_CONTAINER || isInnerType(je)) {
						setExpanded(i, false);
						return;
					}
				}
			}
			super.internalExpandToLevel(node, level);
		}
		
		private boolean isInnerType(IJavaElement element) {
			if (element != null && element.getElementType() == IJavaElement.TYPE) {
				IType type= (IType)element;
				try {
					return type.isMember();
				} catch (JavaModelException e) {
					IJavaElement parent= type.getParent();
					if (parent != null) {
						int parentElementType= parent.getElementType();
						return (parentElementType != IJavaElement.COMPILATION_UNIT && parentElementType != IJavaElement.CLASS_FILE);
					}
				}
			}
			return false;		
		}
	}
	
	private class OutlineContentProvider extends StandardJavaElementContentProvider {