[Dialog] Also take fixed element into account

[oliviertassinari]

Closes #7096

• PR has tests / docs demo, and is linted.
• Commit and PR titles begin with [ComponentName], and are in imperative form: "[Component] Fix leaky abstraction".
• Description explains the issue / use-case resolved, and auto-closes the related issue(s) (http://tr.im/vFqem).

[dsaco]

just now i upgrade to1.0.0-beta.2 (windows system , chrome browser)
it's remove popover and use menu
the problem is : if the body is long and has vertical scrollbar it's ok,
when the boby is short, add padding-right to body
every open cause the page layout change (a little strange)
follow is picture
short body normal
short body open menu
is this a right thing ? if you can understand this words , please reply me

[oliviertassinari]

I'm not sure, it would be great to have a reproduction example.

[dsaco]

upload code take some times...
this is the demo sandbox

[oliviertassinari]

@dsaco Sounds like an issue yes. It would be perfect to have a small reproduction example on codesandbox or webpackbin to further investigate.

[dsaco]

this is codesandbox url