Use active window if on current workspace for fullscreen mode.
BUG=330566,340647
TEST=WindowSelectorTest.FullscreenWindow,RootWindowControllerTest.GetWindowForFullscreenMode,RootWindowControllerTest.MultipleDisplaysGetWindowForFullscreenMode,PanelWindowResizerTest.AttachToSecondFullscreenDisplay
TEST=Open a panel and navigate a browser to an html5 fullscreen page, and fullscreen it. Alt+tab to the panel, should be able to see the panel.
Review URL: https://codereview.chromium.org/
149493008
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253794 0039d316-1c4b-4281-b951-d872f2087c98