test: Add desktopui_WindowManagerFocusNewWindows.

This uses the new Python version of autox to open
a few windows and check that the window manager
moves them onscreen and focuses them.  Note that
it doesn't actually check what gets composited,
though (although that should soon be pretty
straightforward to add).

BUG=chromium-os:2041,chromium-os:2229
TEST=ran it on x86-generic

Review URL: http://codereview.chromium.org/1371003
6 files changed