Avoid hiding a docked window when it is going to get fullscreened

BUG=309955

Review URL: https://codereview.chromium.org/38603002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230683 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230683