clean up core/layout.js

Author: samouri

src/core/layout.js

@@ -16,16 +16,6 @@
 
 import {devAssertElement} from './assert';
 
-/**
- * Whether the tag is an internal (service) AMP tag.
- * @param {!Element|string} tag
- * @return {boolean}
- */
-function isInternalElement(tag) {
-  const tagName = typeof tag == 'string' ? tag : tag.tagName;
-  return !!(tagName && tagName.toLowerCase().startsWith('i-'));
-}
-
 /**
  * Returns "true" for internal AMP nodes or for placeholder elements.
  * @param {!Node} node
@@ -37,7 +27,7 @@ export function isInternalOrServiceNode(node) {
   }
   node = devAssertElement(node);
 
-  if (isInternalElement(node)) {
+  if (node.tagName.toLowerCase().startsWith('i-')) {
     return true;
   }
   if (