app/node_modules/@angular/material/form-field/_mdc-text-field-textarea-overrides.scss

// MDCs default textarea styles cannot be used because they only apply if a special
// class is applied to the "mdc-text-field" wrapper. Since we cannot know whether the
// registered form-field control is a textarea and MDC by default does not have styles
// for textareas in the fill appearance, we add our own minimal textarea styles
// which are scoped to the actual textarea element (i.e. not require a class in the
// text-field wrapper) and integrate better with the any configured appearance.

// Mixin that can be included to override the default MDC text-field styles
// to properly support textareas.
@mixin private-text-field-textarea-overrides() {
  // Ensures that textarea elements inside of the form-field have proper vertical spacing
  // to account for the floating label. Also ensures that there is no vertical text overflow.
  // **Note**: Before changing this selector, make sure the `cdk-textarea-autosize` class is
  // still able to override the `resize` property to `none`.
  .mat-mdc-form-field-textarea-control {
    // Set the vertical alignment for textareas inside form fields to be the middle. This
    // ensures that textareas do not stretch the infix container vertically without having
    // multiple rows of text. See: https://github.com/angular/components/pull/22089.
    vertical-align: middle;
    // Textareas by default also allow users to resize the textarea horizontally. This
    // causes the textarea to overflow the form-field. We only allow vertical resizing.
    resize: vertical;
    box-sizing: border-box;
    height: auto;
    // Using padding for textareas causes a bad user experience because the text outside
    // of the text box will overflow vertically. Also, the vertical spacing for controls
    // is set through the infix container to allow for arbitrary form-field controls.
    margin: 0;
    padding: 0;
    border: none;

    // By default IE always renders scrollbars on textarea.
    // This brings it in line with other browsers.
    overflow: auto;
  }
}