Brandon Yanofsky

#### Problem The [`MatTabGroup`](https://material.angular.io/components/tabs/overview) component encapsulates both the tab header and tab body. Observe that [the tab group template](https://github.com/angular/components/blob/b4422978da053623320f72f62dc6fd9e533fc54a/src/material/tabs/tab-group.html) is composed of two components: [MatTabHeader](https://github.com/angular/components/blob/master/src/material/tabs/tab-group.html#L1-L34) and [MatTabBody](https://github.com/angular/components/blob/master/src/material/tabs/tab-group.html#L36-L53). Both of these...

Updating design based on discussions with @andrewseguin. 2 new components will be extracted from `MatTabGroup`. They are `MatTabList` and `MatTabPanel` (to match naming of the [ARIA pattern](https://www.w3.org/TR/wai-aria-practices-1.1/#tabpanel)). Both components will...