[ShadyCSS] Too specific slotted(*) causes unexpected styling

Here's an example of what I've found when styling in Polymer, although I assume the problem is with shady polyfill itself

I have a container element with a slot and default style for all slotted elements. It's important that I select the slotted element by id

``` html

section#sn :slotted(*) {
color: red;
}

```

In another element I distribute a node and apply same rule in Light DOM

``` html

p {
color: green;
}

Green text

```

**Expected behaviour**

The paragraph should be green

**Actual behaviour**

In browsers using polyfill it will be red.

Attached is the above example

[my-app.html.zip](https://github.com/webcomponents/shadycss/files/1640494/my-app.html.zip)

**Workaround**

When selecting the slotted element one has to be very careful not be too specific. Above even if changed to using class `section.slot ::slotted(*)` alone won't help without making the selector in `my-app` more specific like.

``` css
my-container p {
color: green;
}
```

Otherwise the naked `p` selector will still be too little specific.