Fix ListViewEventsTests outside of IE #134
Fix ListViewAnimation2Test outside of IE #134

There were a few problems:
- ListView styles in unit test had to be updated to account for the
  default -200px padding (the test's styles assumed the default padding
  was 0).
- Our technique of using win-proxy to prevent margin collapsing between
  the win-surface and the win-groupheadercontainer does not work in
  Safari. Fixed this by taking advantage of Safari's
  -webkit-margin-collapse CSS attribute.
- When a group header was unvirtualized, the win-groupheadercontainer was
  collapsing causing all of the items to shift. The fix is to set the size
  of the scrolling dimension of the win-groupheadercontainers for inline
  headers (width for horizontal layouts, height for vertical layouts).
  This matches what the layouts do when using CSS grid.
Fix surface length outside of IE #134

win-surface needs to be inline-flex instead of inline-grid so that it
sizes to its content rather than to its parent. This matches the
display: inline-grid style found in IE.
Enable more ListView tests outside of IE #134