Fix WindowTreeHostManager::GetPrimaryRootWindow.

ash/display/window_tree_host_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/display/window_tree_host_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <map>
 #include <memory>
@@ skipping 310 matching lines @@
   observers_.RemoveObserver(observer);
 }
 
 // static
 int64_t WindowTreeHostManager::GetPrimaryDisplayId() {
   CHECK_NE(display::kInvalidDisplayId, primary_display_id);
   return primary_display_id;
 }
 
 aura::Window* WindowTreeHostManager::GetPrimaryRootWindow() {
+  // If |primary_tree_host_for_replace_| is set, it means |primary_display_id|
+  // is kInvalidDisplayId.
+  if (primary_tree_host_for_replace_)
+    return GetWindow(primary_tree_host_for_replace_);
   return GetRootWindowForDisplayId(primary_display_id);
 }
 
 aura::Window* WindowTreeHostManager::GetRootWindowForDisplayId(int64_t id) {
   AshWindowTreeHost* host = GetAshWindowTreeHostForDisplayId(id);
   return host ? GetWindow(host) : nullptr;
 }
 
 AshWindowTreeHost* WindowTreeHostManager::GetAshWindowTreeHostForDisplayId(
     int64_t display_id) {
@@ skipping 284 matching lines @@
 }
 
 void WindowTreeHostManager::DeleteHost(AshWindowTreeHost* host_to_delete) {
   ClearDisplayPropertiesOnHost(host_to_delete);
   RootWindowController* controller =
       GetRootWindowController(GetWindow(host_to_delete));
   DCHECK(controller);
   controller->MoveWindowsTo(GetPrimaryRootWindow());
   // Delete most of root window related objects, but don't delete
   // root window itself yet because the stack may be using it.
   controller->Shutdown();

[oshima, 2017/05/12 00:19:21]

can you reset the primary_tree_host_for_replace_ if it's same as host_to_delete
here?

[wutao, 2017/05/12 00:43:57]

Done.

   base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, controller);
 }
 
 void WindowTreeHostManager::OnDisplayRemoved(const display::Display& display) {
   AshWindowTreeHost* host_to_delete = window_tree_hosts_[display.id()];
   CHECK(host_to_delete) << display.ToString();
 
   // When the primary root window's display is removed, move the primary
   // root to the other display.
   if (primary_display_id == display.id()) {
@@ skipping 209 matching lines @@
 
   window_tree_hosts_[display.id()] = ash_host;
   SetDisplayPropertiesOnHost(ash_host, display);
 
   if (switches::ConstrainPointerToRoot())
     ash_host->ConfineCursorToRootWindow();
   return ash_host;
 }
 
 }  // namespace ash