bug(mat-tab-group): inner div cannot cover 100% of viewport, on iphone

#### Reproduction

Use StackBlitz to reproduce your issue: https://stackblitz.com/fork/components-issue
StackBlitz to reproduce:
https://stackblitz.com/edit/components-issue-dssxxk
or
https://stackblitz.com/edit/angular-3qr9lv

Attention - this will reproduce only on iOS (e.g. iPhone) with both Chrome and Safari.
On Android it works perfectly.
On computer with Chrome and F12 on - it works perfectly.

Steps to reproduce:
1. Create mat-tab-group with few mat-tab children.
2. Inside one of the children, set a div with 100% height, 100% width, fixed position, with top, right equal to zero and a high z-index. Also, set it with a background-color (e.g. blue) to easily reproduce the behavior.


#### Expected Behavior

What behavior were you expecting to see?
The created div should cover ALL viewport (top to bottom, right to left), including the mat-tab, mat-tab-group and any other components on the HTML page (e.g. navbar etc.)
In other words - all screen will be blue.

#### Actual Behavior

What behavior did you actually see?
The created div covers the entire page, but you cannot see it, although it has a blue background, the blue color appears only within the mat-tab. above the mat-tab it doesn't show the blue background, yet it covers the elements (e.g. if you have a button above the mat-tab-group, you cannot click it)

#### Environment

- Angular: 8
- CDK/Material: 8
- Browser(s): chrome, safari
- Operating System (e.g. Windows, macOS, Ubuntu): iOS

从链接的 StackBlitz 复现开始，在 iOS 上分别使用 Chrome 和 Safari 运行它们，然后将 mat-tab-group 的行为与 Android 或桌面端进行比较。跟踪涉及覆盖 viewport 的内部 div 的 mat-tab-group 布局和定位。完成标准是：div 能够明显覆盖整个 viewport，包括选项卡组外部的内容，同时不改变其他平台上所述的行为。

由索引模型根据 Issue 内容生成。