fix(cdk/text-field): Long multiline textfield focus issue.

When we have long multiline textfield and put cursor on almost an end (For eg. on 3rd last line) the scroll moves up to the top of textarea. This fix will listen to scroll event and update the `scrollTop` in `resizeToFitContent` method

Fixes #20255

Author: mistrykaran91

src/cdk/text-field/autosize.ts

@@ -47,6 +47,7 @@ export class CdkTextareaAutosize implements AfterViewInit, DoCheck, OnDestroy {
 
   /** Keep track of the previous textarea value to avoid resizing when the value hasn't changed. */
   private _previousValue?: string;
+  private _currentScrollTop: number;
   private _initialHeight: string | undefined;
   private readonly _destroyed = new Subject<void>();
   private _listenerCleanups: (() => void)[] | undefined;
@@ -164,6 +165,7 @@ export class CdkTextareaAutosize implements AfterViewInit, DoCheck, OnDestroy {
           this._renderer.listen('window', 'resize', () => this._resizeEvents.next()),
           this._renderer.listen(this._textareaElement, 'focus', this._handleFocusEvent),
           this._renderer.listen(this._textareaElement, 'blur', this._handleFocusEvent),
+          this._renderer.listen(this._textareaElement, 'scroll', this._handleScrollEvent),
         ];
         this._resizeEvents.pipe(auditTime(16)).subscribe(() => {
           // Clear the cached heights since the styles can change
@@ -284,6 +286,10 @@ export class CdkTextareaAutosize implements AfterViewInit, DoCheck, OnDestroy {
     this._hasFocus = event.type === 'focus';
   };
 
+  private _handleScrollEvent = (event: Event) => {
+    this._currentScrollTop = (event?.target as HTMLTextAreaElement)?.scrollTop;
+  };
+
   ngDoCheck() {
     if (this._platform.isBrowser) {
       this.resizeToFitContent();
@@ -323,6 +329,7 @@ export class CdkTextareaAutosize implements AfterViewInit, DoCheck, OnDestroy {
 
     // Use the scrollHeight to know how large the textarea *would* be if fit its entire value.
     textarea.style.height = `${height}px`;
+    textarea.scrollTop = this._currentScrollTop;
 
     this._ngZone.runOutsideAngular(() => {
       if (typeof requestAnimationFrame !== 'undefined') {