[test] test:unit fails with ?wc-shadydom=true&wc-ce=true options

[t2ym]

[test] test:unit fails with ?wc-shadydom=true&wc-ce=true options

Suspected Root Cause

• ShadyDOM polyfill is not working well
  • Updating to the latest @webcomponents/shadycss@1.8.0 but still reproducible

Error Message

wct-mocha.js:2384 Error stamping 
<template>​#document-fragment<counter-element>​</counter-element>​</template>​
TypeError: window.ShadyCSS.ScopingShim.prepareAdoptedCssText is not a function
    at HTMLElement.adoptStyles (lit-element.ts:140)
    at HTMLElement.initialize (lit-element.ts:95)
    at new UpdatingElement (updating-element.ts:253)
    at new LitElement (lit-element.ts:25)
    at new MixinClass (i18n.js:48)
    at new I18nBaseElement (i18n.js:100)
    at new CounterElement (counter-element.js:67)
    at ye (CustomElementInternals.js:266)
    at Q.e (CustomElementInternals.js:177)
    at Q (CustomElementInternals.js:231)

Workaround

• Skip ShadyDOM tests