Fix TabStripTest for Refresh.

This patch fixes various tests in the TabStripTest suite:
* VisibilityInOverflow and TabForEventWhenStacked were broken because
  Refresh tabs are larger than before, and the test wasn't allocating
  enough room for them.
* TabCloseButtonVisibilityWhenNotStacked was broken because in Refresh
  close buttons on inactive tabs are never visible unless the tab is
  hovered. To fix this, the test now hovers the tab.
* TabCloseButtonVisibilityWhenStacked was broken for the previous
  reason but also because close buttons shouldn't be shown on inactive
  tabs in stacked layout ever.

Bug: 846410
Change-Id: I49655b9e03ba9622b71c6a0110e6772f72c0e8e5
Reviewed-on: https://chromium-review.googlesource.com/1092153
Commit-Queue: Bret Sepulveda <bsep@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565811}
2 files changed