Nested Expansion panels keep overflow visible

[Tommatheussen]

Bug, feature request, or proposal:

Bug

What is the expected behavior?

Nested Expansion panels should collapse their content, and set the overflow to hidden.

What is the current behavior?

Nested expansion panels collapse their content, but overflow is kept as visible, showing a scrollbar and nasty empty space.

What are the steps to reproduce?

Providing a StackBlitz/Plunker (or similar) is the best way to get the team to see your issue.

Plunker starter (using on @master): http://plnkr.co/edit/uVmKf7NTB9ZVUSv2IyGR?p=preview

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

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

Angular 5.0.4
Material 5.0.0-rc.2
MacOS
TS 2.4.2
Browser: Seen in Safari, Chrome and Firefox (not tested any others)

Is there anything else we should know?

This only seems to be actually noticeable when used inside tabs. Checking the dev tools, I can see the .mat-expanded class from the parent causes the child to keep it's overflow visible

[tarunmp0102]

It is noticed any where in the page, not necessarily only in tabs

[roddy]

Is there a workaround for this pending the pull request being merged?

[bluefire2121]

#5269

[josephperrott]

Fixed by #10138