[MatSidenav] Sidenav Toggling Can Cause Content Shifting

#### Bug, feature request, or proposal:
Bug

#### What is the expected behavior?
Mat-sidenav-content is not moved from original position upon quick mat-sidenav toggles

#### What is the current behavior?
Quick mat-sidenav toggles can cause mat-sidenav-content to be shifted over until the drawer is toggled again

#### What are the steps to reproduce?

Set the autofocus on mat-sidenav to true, and place a focusable input in the mat-sidenav
Click the 'open drawer' button quickly and repeatedly until the content shifts. Click the button again and the content will shift back.

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

#### What is the use-case or motivation for changing an existing behavior?
Use-case: User accidentally opens the drawer and quickly presses again to undo the action. This will result in possibly all content on the page not being displayed.

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?
Angular: 6.0.9
Material: 6.4.1

首先，在启用 autofocus 且 MatSidenav 内包含可聚焦 input 的情况下，复现链接 StackBlitz 中的行为，然后检查快速切换期间 MatSidenav 和 mat-sidenav-content 的行为。完成的标准是，重复执行打开和关闭操作后，mat-sidenav-content 不再保持偏移状态，并且不需要再次切换即可恢复其位置。

由索引模型根据 Issue 内容生成。