rc5 md-dialog fullscreen works only for small screen

[stunaz]

why add the media condition @media (max-width: $layout-breakpoint-sm)

@media (max-width: $layout-breakpoint-sm) {
  md-dialog.md-dialog-fullscreen {
    min-height: 100%;
    min-width: 100%;
    border-radius: 0;
  }
}

This means we can't force a full screen on a big screen

[devversion]

I think this is by intention. See at the Material Specs (http://www.google.com/design/spec/components/dialogs.html#dialogs-full-screen-dialogs)

References #5793