Remove unused parameter in ash::WindowResizer::CompleteDrag()

BUG=None
TEST=None
TBR=oshima

Review URL: https://codereview.chromium.org/122093003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242694 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242694