Fix VK animation related issues

This CL did the following things:
1. changes targeting opacity from 0 to 0.2 during hide animation
2. fix "regain focus before hide animation finish, VK doesn't show up" issue

BUG=333284

Review URL: https://codereview.chromium.org/134133003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245340 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245340