Tests that distributed nodes and their updates are correctly shown in different shadow host display modes.

========= Original ========
- <div id="shadowHost">
      <div slot="distributeMeToYoungest">\n        youngest distributed text\n    </div>
      <div slot="distributeMeToOldest">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
  </div>
========= After shadow root created ========
- <div id="shadowHost">
    - #shadow-root (open)
        - <div class="oldestShadowMain">
            - <slot name=".distributeMeToOldest">
                  <div id="fallbackOldest"></div>
              </slot>
          </div>
      <div slot="distributeMeToYoungest">\n        youngest distributed text\n    </div>
      <div slot="distributeMeToOldest">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
  </div>
========= After adding distributed node ========
- <div id="shadowHost">
    - #shadow-root (open)
        - <div class="oldestShadowMain">
            - <slot name=".distributeMeToOldest">
                  <div id="fallbackOldest"></div>
              </slot>
          </div>
      <div slot="distributeMeToYoungest">\n        youngest distributed text\n    </div>
      <div slot="distributeMeToOldest">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
      <div slot="distributeMeAsWell_1"></div>
  </div>
========= After adding another distributed node ========
- <div id="shadowHost">
    - #shadow-root (open)
        - <div class="oldestShadowMain">
            - <slot name=".distributeMeToOldest">
                  <div id="fallbackOldest"></div>
              </slot>
          </div>
      <div slot="distributeMeToYoungest">\n        youngest distributed text\n    </div>
      <div slot="distributeMeToOldest">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
      <div slot="distributeMeToInner">\n        oldest distributed text\n    </div>
      <div slot="distributeMeAsWell_1"></div>
      <div slot="distributeMeAsWell_2"></div>
  </div>