DevTools: fix old shadow dom in DOMLinkifier

Bug: 929561
Change-Id: I98ec6ea3cc6a6de1d82489a737cd5f51f9bc56f0
Reviewed-on: https://chromium-review.googlesource.com/c/1457919Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Erik Luo <luoe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629953}

third_party/blink/renderer/devtools/front_end/elements/DOMLinkifier.js

@@ -89,7 +89,7 @@ Elements.DOMLinkifier.linkifyDeferredNodeReference = function(deferredNode) {
   const root = createElement('div');
   const shadowRoot = UI.createShadowRootWithCoreStyles(root, 'elements/domLinkifier.css');
   const link = shadowRoot.createChild('div', 'node-link');
-  link.createChild('content');
+  link.createChild('slot');
   link.addEventListener('click', deferredNode.resolve.bind(deferredNode, onDeferredNodeResolved), false);
   link.addEventListener('mousedown', e => e.consume(), false);