test: Add desktopui_WindowManagerFocusNewWindows.

client/bin/site_login.py

Index: client/bin/site_login.py
diff --git a/client/bin/site_login.py b/client/bin/site_login.py
index 7d212fc582bbaf25e26dd9071e379c159f9feda2..51b8a9d842c72ab78ab57b7f28ade6017e4c419b 100644
--- a/client/bin/site_login.py
+++ b/client/bin/site_login.py
@@ -88,6 +88,16 @@ def wait_for_screensaver(timeout=10, raise_error=True):
     return True
 
 
+def wait_for_window_manager(timeout=20):
+    """Wait until the window manager is running."""
+    start_time = time.time()
+    while time.time() - start_time < timeout:
+        if os.system('pgrep ^%s$' % chromeos_constants.WINDOW_MANAGER) == 0:
+            return True
+        time.sleep(0.1)
+    return False
+
+
 def nuke_login_manager():
     nuke_process_by_name('session_manager')
     wait_for_browser()