[ash] drag and drop from app list to shelf is not working in secondary monitor.
Problem:
Callers of ApplicationDragAndDropHost method in ShelfView and AppsGridView
uses root window coordinate.
R=skuhne@chromium.org, benwells@chromium.org, jamescook@chromium.org
BUG=319826
TEST=browser_tests --gtest_filter=LauncherAppBrowserTestWithMultiMonitor.BasicDragAndDrop
Review URL: https://codereview.chromium.org/
68263026
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237668 0039d316-1c4b-4281-b951-d872f2087c98