Revert "fix(material/form-field): outline label position (#29123)" (#29132)

This reverts commit eb22e2e.

(cherry picked from commit 0106420)

Author: crisbeto

src/material/form-field/form-field.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import {Directionality} from '@angular/cdk/bidi';
-import {Platform, _getShadowRoot} from '@angular/cdk/platform';
+import {Platform} from '@angular/cdk/platform';
 import {
   AfterContentChecked,
   AfterContentInit,
@@ -701,13 +701,14 @@ export class MatFormField
   /** Checks whether the form field is attached to the DOM. */
   private _isAttachedToDom(): boolean {
     const element: HTMLElement = this._elementRef.nativeElement;
-    const rootNode = element.getRootNode();
-    // If the element is inside the DOM the root node will be either the document,
-    // the closest shadow root or an element that is not yet rendered, otherwise it'll be the element itself.
-    return (
-      rootNode &&
-      rootNode !== element &&
-      (rootNode === document || rootNode === _getShadowRoot(element))
-    );
+    if (element.getRootNode) {
+      const rootNode = element.getRootNode();
+      // If the element is inside the DOM the root node will be either the document
+      // or the closest shadow root, otherwise it'll be the element itself.
+      return rootNode && rootNode !== element;
+    }
+    // Otherwise fall back to checking if it's in the document. This doesn't account for
+    // shadow DOM, however browser that support shadow DOM should support `getRootNode` as well.
+    return document.documentElement!.contains(element);
   }
 }