DragDrop Autoscroll feature not working with Material Table

Relates to https://github.com/angular/components/pull/16382

#### Reproduction

https://stackblitz.com/edit/angular-qczaca

Steps to reproduce:
1. Try dragging a row to the edge of its container.
2. You can see that Material Table cannot be autoscrolled while a simple container can be... (like the div in the Stackblitz example).

#### Expected Behavior

I can use autoscroll feature with Material Table as well.

#### Actual Behavior

Autoscroll does not work with Material Table.

#### Environment

Angular, CDK/Material:
```
"@angular/animations": "~8.2.0",
"@angular/cdk": "~8.1.2",
"@angular/common": "~8.2.0",
"@angular/compiler": "~8.2.0",
"@angular/core": "~8.2.0",
"@angular/forms": "~8.2.0",
"@angular/material": "^8.1.2",
"@angular/platform-browser": "~8.2.0",
"@angular/platform-browser-dynamic": "~8.2.0",
"@angular/router": "~8.2.0",
"hammerjs": "^2.0.8"
```

```
"@angular-devkit/build-angular": "~0.802.0",
"@angular/cli": "~8.2.0",
"@angular/compiler-cli": "~8.2.0",
"@angular/language-service": "~8.2.0"
```

まず、リンクされた StackBlitz の再現を実行し、シンプルなコンテナでのドラッグ時の自動スクロールと Material Table での動作を比較します。関連する pull request を読んで背景を確認してから、テーブル固有の動作を追跡します。行をコンテナの端までドラッグすると、期待どおりに Material Table が自動スクロールする状態になれば完了です。

索引モデルが issue の本文から書いたものです。