ripples (mat-checkbox, mat-option, etc...) cause scrolling in dialog

#### Bug, feature request, or proposal:
If a mat-checkbox is the last element in a mat-dialog-content it will cause the dialog to to have a scrollbar, even if the content has not reached it's max height.

#### What is the expected behavior?

There should be no scrolling if the dialog has room to grow.

#### What is the current behavior?

The dialog scrolls when a mat-checkbox is present.

#### What are the steps to reproduce?
https://stackblitz.com/edit/angular-material2-issue-dhosn1

Click the button, notice the dialog.

#### What is the use-case or motivation for changing an existing behavior?

It looks bad.

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Whatever is used by stackblitz

#### Is there anything else we should know?

首先在链接的 StackBlitz 示例中重现该问题，然后检查 mat-dialog-content 与 mat-checkbox 的 ripple 之间的交互，尤其是在复选框是最后一个元素时。当存在 mat-checkbox 或类似的带 ripple 组件时，一个仍有扩展空间的对话框不再出现滚动条，即表示完成。

由索引模型根据 Issue 内容生成。