diff --git a/src/cdk/a11y/focus-trap/event-listener-inert-strategy.ts b/src/cdk/a11y/focus-trap/event-listener-inert-strategy.ts
index 5c5be8db7478..8fc31ea17539 100644
--- a/src/cdk/a11y/focus-trap/event-listener-inert-strategy.ts
+++ b/src/cdk/a11y/focus-trap/event-listener-inert-strategy.ts
@@ -8,7 +8,6 @@
 
 import {FocusTrapInertStrategy} from './focus-trap-inert-strategy';
 import {ConfigurableFocusTrap} from './configurable-focus-trap';
-import {closest} from './polyfill';
 
 /**
  * Lightweight FocusTrapInertStrategy that adds a document focus event
@@ -53,7 +52,8 @@ export class EventListenerFocusTrapInertStrategy implements FocusTrapInertStrate
 
     // Don't refocus if target was in an overlay, because the overlay might be associated
     // with an element inside the FocusTrap, ex. mat-select.
-    if (!focusTrapRoot.contains(target) && closest(target, 'div.cdk-overlay-pane') === null) {
+    if (target && !focusTrapRoot.contains(target) &&
+        target.closest('div.cdk-overlay-pane') === null) {
         // Some legacy FocusTrap usages have logic that focuses some element on the page
         // just before FocusTrap is destroyed. For backwards compatibility, wait
         // to be sure FocusTrap is still enabled before refocusing.
diff --git a/src/cdk/a11y/focus-trap/focus-trap.ts b/src/cdk/a11y/focus-trap/focus-trap.ts
index 737c6fc9e795..31c6ac98e611 100644
--- a/src/cdk/a11y/focus-trap/focus-trap.ts
+++ b/src/cdk/a11y/focus-trap/focus-trap.ts
@@ -271,12 +271,10 @@ export class FocusTrap {
       return root;
     }
 
-    // Iterate in DOM order. Note that IE doesn't have `children` for SVG so we fall
-    // back to `childNodes` which includes text nodes, comments etc.
-    let children = root.children || root.childNodes;
+    const children = root.children;
 
     for (let i = 0; i < children.length; i++) {
-      let tabbableChild = children[i].nodeType === this._document.ELEMENT_NODE ?
+      const tabbableChild = children[i].nodeType === this._document.ELEMENT_NODE ?
         this._getFirstTabbableElement(children[i] as HTMLElement) :
         null;
 
@@ -295,10 +293,10 @@ export class FocusTrap {
     }
 
     // Iterate in reverse DOM order.
-    let children = root.children || root.childNodes;
+    const children = root.children;
 
     for (let i = children.length - 1; i >= 0; i--) {
-      let tabbableChild = children[i].nodeType === this._document.ELEMENT_NODE ?
+      const tabbableChild = children[i].nodeType === this._document.ELEMENT_NODE ?
         this._getLastTabbableElement(children[i] as HTMLElement) :
         null;
 
diff --git a/src/cdk/a11y/focus-trap/polyfill.ts b/src/cdk/a11y/focus-trap/polyfill.ts
deleted file mode 100644
index cd89b3900251..000000000000
--- a/src/cdk/a11y/focus-trap/polyfill.ts
+++ /dev/null
@@ -1,40 +0,0 @@
-/**
- * @license
- * Copyright Google LLC All Rights Reserved.
- *
- * Use of this source code is governed by an MIT-style license that can be
- * found in the LICENSE file at https://angular.io/license
- */
-
-/** IE 11 compatible closest implementation that is able to start from non-Element Nodes. */
-export function closest(element: EventTarget|Element|null|undefined, selector: string):
-    Element|null {
-  if (!(element instanceof Node)) { return null; }
-
-  let curr: Node|null = element;
-  while (curr != null && !(curr instanceof Element)) {
-    curr = curr.parentNode;
-  }
-
-  return curr && (hasNativeClosest ?
-      curr.closest(selector) : polyfillClosest(curr, selector)) as Element|null;
-}
-
-/** Polyfill for browsers without Element.closest. */
-function polyfillClosest(element: Element, selector: string): Element|null {
-  let curr: Node|null = element;
-  while (curr != null && !(curr instanceof Element && matches(curr, selector))) {
-    curr = curr.parentNode;
-  }
-
-  return (curr || null) as Element|null;
-}
-
-const hasNativeClosest = typeof Element != 'undefined' && !!Element.prototype.closest;
-
-/** IE 11 compatible matches implementation. */
-function matches(element: Element, selector: string): boolean {
-  return element.matches ?
-      element.matches(selector) :
-      (element as any)['msMatchesSelector'](selector);
-}