Use WindowTracker when resizing root window as it may delete other window in unit tests.

ash/wm/root_window_layout_manager.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/wm/root_window_layout_manager.h"
 
 #include "ash/desktop_background/desktop_background_widget_controller.h"
 #include "ash/root_window_controller.h"
 #include "ui/aura/window_event_dispatcher.h"
+#include "ui/aura/window_tracker.h"
 #include "ui/compositor/layer.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 
 ////////////////////////////////////////////////////////////////////////////////
 // RootWindowLayoutManager, public:
 
 RootWindowLayoutManager::RootWindowLayoutManager(aura::Window* owner)
     : owner_(owner) {
 }
 
 RootWindowLayoutManager::~RootWindowLayoutManager() {
 }
 
 
 ////////////////////////////////////////////////////////////////////////////////
 // RootWindowLayoutManager, aura::LayoutManager implementation:
 
 void RootWindowLayoutManager::OnWindowResized() {
   gfx::Rect fullscreen_bounds =
       gfx::Rect(owner_->bounds().width(), owner_->bounds().height());
 
   // Resize both our immediate children (the containers-of-containers animated
   // by PowerButtonController) and their children (the actual containers).
-  aura::Window::Windows::const_iterator i;
-  for (i = owner_->children().begin(); i != owner_->children().end(); ++i) {
-    (*i)->SetBounds(fullscreen_bounds);
-    aura::Window::Windows::const_iterator j;
-    for (j = (*i)->children().begin(); j != (*i)->children().end(); ++j)
-      (*j)->SetBounds(fullscreen_bounds);
+  aura::WindowTracker children_tracker(owner_->children());
+  while (children_tracker.has_windows()) {
+    aura::Window* child = children_tracker.Pop();
+    child->SetBounds(fullscreen_bounds);
+    aura::WindowTracker grandchildren_tracker(child->children());
+    while (grandchildren_tracker.has_windows())

[sky, 2015/12/02 22:01:04]

WindowTracker internally uses a set. The old code use the child order in a
vector. This means you're subtley changing the order of the resize, and in a
non-deterministic way. I think we should keep it the way we had it.

[oshima, 2015/12/03 05:50:12]

Good point. I changed WT to use vector instead.

+      grandchildren_tracker.Pop()->SetBounds(fullscreen_bounds);
   }
   RootWindowController* root_window_controller =
       GetRootWindowController(owner_);
   DesktopBackgroundWidgetController* background =
       root_window_controller->wallpaper_controller();
 
   if (!background && root_window_controller->animating_wallpaper_controller()) {
     background = root_window_controller->animating_wallpaper_controller()->
         GetController(false);
   }
@@ skipping 16 matching lines @@
     bool visible) {
 }
 
 void RootWindowLayoutManager::SetChildBounds(
     aura::Window* child,
     const gfx::Rect& requested_bounds) {
   SetChildBoundsDirect(child, requested_bounds);
 }
 
 }  // namespace ash