Exclude a couple types of windows from CrOS Alt+Tab.

ash/common/wm/window_cycle_controller.cc

Index: ash/common/wm/window_cycle_controller.cc
diff --git a/ash/common/wm/window_cycle_controller.cc b/ash/common/wm/window_cycle_controller.cc
index 2b8ccc9ddf1efc592056e199d1d62a28d136cbfc..686290e54064664a3af0ddb3f256598b5223de62 100644
--- a/ash/common/wm/window_cycle_controller.cc
+++ b/ash/common/wm/window_cycle_controller.cc
@@ -9,6 +9,7 @@
 #include "ash/common/wm/mru_window_tracker.h"
 #include "ash/common/wm/window_cycle_event_filter.h"
 #include "ash/common/wm/window_cycle_list.h"
+#include "ash/common/wm/window_state.h"
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
 #include "ash/public/cpp/shell_window_ids.h"
@@ -54,18 +55,24 @@ void WindowCycleController::HandleCycleWindow(Direction direction) {
 void WindowCycleController::StartCycling() {
   MruWindowTracker::WindowList window_list =
       WmShell::Get()->mru_window_tracker()->BuildMruWindowList();
-  // Exclude the AppList window, which will hide as soon as cycling starts
-  // anyway. It doesn't make sense to count it as a "switchable" window, yet
-  // a lot of code relies on the MRU list returning the app window. If we
-  // don't manually remove it, the window cycling UI won't crash or misbehave,
-  // but there will be a flicker as the target window changes.
+  // Exclude windows:
+  // - non user positionable windows, such as extension popups.
+  // - windows being dragged
+  // - the AppList window, which will hide as soon as cycling starts
+  //   anyway. It doesn't make sense to count it as a "switchable" window, yet
+  //   a lot of code relies on the MRU list returning the app window. If we
+  //   don't manually remove it, the window cycling UI won't crash or misbehave,
+  //   but there will be a flicker as the target window changes. Also exclude
+  //   unselectable windows such as extension popups.
+  auto window_is_ineligible = [](WmWindow* window) {
+    wm::WindowState* state = window->GetWindowState();
+    return !state->IsUserPositionable() || state->is_dragged() ||
+           window->GetRootWindow()
+               ->GetChildByShellWindowId(kShellWindowId_AppListContainer)
+               ->Contains(window);
+  };
   window_list.erase(std::remove_if(window_list.begin(), window_list.end(),
-                                   [](WmWindow* window) {
-                                     return window->GetRootWindow()
-                                         ->GetChildByShellWindowId(
-                                             kShellWindowId_AppListContainer)
-                                         ->Contains(window);
-                                   }),
+                                   window_is_ineligible),
                     window_list.end());
 
   active_window_before_window_cycle_ = GetActiveWindow(window_list);