Avoid trying to layout the desktop when its size is set to 0x0 when minimized on Windows.

ui/aura/desktop.cc

Index: ui/aura/desktop.cc
===================================================================
--- ui/aura/desktop.cc	(revision 110097)
+++ ui/aura/desktop.cc	(working copy)
@@ -323,12 +323,14 @@
 }
 
 void Desktop::SetActiveWindow(Window* window, Window* to_focus) {
+  if (!window)
+    return;
   // The stacking client may impose rules on what window configurations can be
   // activated or deactivated.
-  if (window && !stacking_client_->CanActivateWindow(window))
+  if (!stacking_client_->CanActivateWindow(window))
     return;
   // The window may not be activate-able.
-  if (window && !window->CanActivate())
+  if (!window->CanActivate())
     return;
   // Nothing may actually have changed.
   if (active_window_ == window)