wm: Fix comment after http://codereview.chromium.org/3023034
wm: Fix comment after http://codereview.chromium.org/3023034

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/2808097

joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager