Make sure primary root window is deleted last.

ash/display/display_controller.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/display/display_controller.h"
 
 #include <algorithm>
 #include <cmath>
 #include <map>
 
 #include "ash/ash_switches.h"
 #include "ash/display/cursor_window_controller.h"
 #include "ash/display/display_layout_store.h"
 #include "ash/display/display_manager.h"
 #include "ash/display/mirror_window_controller.h"
 #include "ash/display/root_window_transformers.h"
 #include "ash/display/virtual_keyboard_window_controller.h"
 #include "ash/host/ash_window_tree_host.h"
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/root_window_transformer.h"
 #include "ash/root_window_controller.h"
 #include "ash/root_window_settings.h"
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/shell_delegate.h"
 #include "ash/wm/coordinate_conversion.h"
 #include "base/command_line.h"
+#include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_property.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/aura/window_tree_host.h"
@@ skipping 221 matching lines @@
 void DisplayController::Shutdown() {
   // Unset the display manager's delegate here because
   // DisplayManager outlives DisplayController.
   Shell::GetInstance()->display_manager()->set_delegate(NULL);
 
   cursor_window_controller_.reset();
   mirror_window_controller_.reset();
   virtual_keyboard_window_controller_.reset();
 
   Shell::GetScreen()->RemoveObserver(this);
-  // Delete all root window controllers, which deletes root window
-  // from the last so that the primary root window gets deleted last.

[oshima, 2014/08/30 00:50:36]

This comment was wrong, although deleting primary display will
reassign the primary, so it shouldn't cause a crash.

This is a speculative fix as I couldn't find a repro step/path. 

-  for (WindowTreeHostMap::const_reverse_iterator it =
-           window_tree_hosts_.rbegin();
-       it != window_tree_hosts_.rend();
-       ++it) {
-    RootWindowController* controller =
-        GetRootWindowController(GetWindow(it->second));
-    DCHECK(controller);
-    delete controller;
+
+  int64 primary_id = Shell::GetScreen()->GetPrimaryDisplay().id();
+
+  // Delete non primary root window controllers first, then
+  // delete the primary root window controller.
+  aura::Window::Windows root_windows = DisplayController::GetAllRootWindows();
+  std::vector<RootWindowController*> to_delete;
+  RootWindowController* primary_rwc = NULL;
+  for (aura::Window::Windows::iterator iter = root_windows.begin();
+       iter != root_windows.end();
+       ++iter) {
+    RootWindowController* rwc = GetRootWindowController(*iter);
+    if (GetRootWindowSettings(*iter)->display_id == primary_id)
+      primary_rwc = rwc;
+    else
+      to_delete.push_back(rwc);
   }
+  CHECK(primary_rwc);
+
+  STLDeleteElements(&to_delete);
+  delete primary_rwc;
 }
 
 void DisplayController::CreatePrimaryHost(
     const AshWindowTreeHostInitParams& init_params) {
   const gfx::Display& primary_candidate =
       GetDisplayManager()->GetPrimaryDisplayCandidate();
   primary_display_id = primary_candidate.id();
   CHECK_NE(gfx::Display::kInvalidDisplayID, primary_display_id);
   AddWindowTreeHostForDisplay(primary_candidate, init_params);
 }
@@ skipping 28 matching lines @@
 int64 DisplayController::GetPrimaryDisplayId() {
   CHECK_NE(gfx::Display::kInvalidDisplayID, primary_display_id);
   return primary_display_id;
 }
 
 aura::Window* DisplayController::GetPrimaryRootWindow() {
   return GetRootWindowForDisplayId(primary_display_id);
 }
 
 aura::Window* DisplayController::GetRootWindowForDisplayId(int64 id) {
-  DCHECK_EQ(1u, window_tree_hosts_.count(id));
+  CHECK_EQ(1u, window_tree_hosts_.count(id));

[oshima, 2014/08/30 00:50:36]

I changed to CHECK to catch the error early in release build.

   AshWindowTreeHost* host = window_tree_hosts_[id];
   CHECK(host);
   return GetWindow(host);
 }
 
 void DisplayController::CloseChildWindows() {
   for (WindowTreeHostMap::const_iterator it = window_tree_hosts_.begin();
        it != window_tree_hosts_.end();
        ++it) {
     aura::Window* root_window = GetWindow(it->second);
@@ skipping 436 matching lines @@
     std::string name =
         root_windows[i] == primary ? "aura_root_0" : "aura_root_x";
     gfx::AcceleratedWidget xwindow =
         root_windows[i]->GetHost()->GetAcceleratedWidget();
     XStoreName(gfx::GetXDisplay(), xwindow, name.c_str());
   }
 #endif
 }
 
 }  // namespace ash