GitLab

The following issues have been fixed:
1) If one or more panels in the stack are collapsed, the live preview is not shown correctly.
2) If the whole stack is minimized by the system, the live preview is not shown correctly.

BUG=177743
TEST=Manual tests by collapsing a panel or system-minimzing a stack and then hover over the taskbar icon

Review URL: https://chromiumcodereview.appspot.com/16035007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@203016 0039d316-1c4b-4281-b951-d872f2087c98