cros: restore bounds on Dis{Re}Connect & Off{On} mirror mode

changes:
- WindowState caches a member for saving PersistentWindowInfo, which is
  saved on OnWillProcessDisplayChanges() and restored on
  OnDisplayConfigurationChanged().
- Saving when it hasn't been saved.
- Restoring when (1) we have saved persistent info, (2) persistent
  display id is a valid display currently, (3) persistent display id
  is not current display id. We could have display position/layout
  changes, in which case we transform the window accordingly.
- Reset saved PersistentWindowInfo each time window bounds have restored
  or when bounds changed by user.

Bug: 805046
Test: ash_unittests --gtest_filter=PersistentWindowControllerTest*
Change-Id: I67426ca17f0d25f92284eb690f849bf77bb748be
Reviewed-on: https://chromium-review.googlesource.com/893644Reviewed-by: Mitsuru Oshima (In Tokyo) <oshima@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Qiang Xu <warx@google.com>
Cr-Commit-Position: refs/heads/master@{#537849}

ash/BUILD.gn

@@ -133,6 +133,10 @@ component("ash") {
     "display/null_mouse_warp_controller.h",
     "display/overscan_calibrator.cc",
     "display/overscan_calibrator.h",
+    "display/persistent_window_controller.cc",
+    "display/persistent_window_controller.h",
+    "display/persistent_window_info.cc",
+    "display/persistent_window_info.h",
     "display/projecting_observer_chromeos.cc",
     "display/projecting_observer_chromeos.h",
     "display/resolution_notification_controller.cc",
@@ -1373,6 +1377,7 @@ test("ash_unittests") {
     "display/extended_mouse_warp_controller_unittest.cc",
     "display/mirror_window_controller_unittest.cc",
     "display/mouse_cursor_event_filter_unittest.cc",
+    "display/persistent_window_controller_unittest.cc",
     "display/projecting_observer_chromeos_unittest.cc",
     "display/resolution_notification_controller_unittest.cc",
     "display/root_window_transformers_unittest.cc",

ash/display/persistent_window_controller.cc

+// Copyright 2018 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/persistent_window_controller.h"
+
+#include "ash/display/persistent_window_info.h"
+#include "ash/public/cpp/ash_switches.h"
+#include "ash/session/session_controller.h"
+#include "ash/shell.h"
+#include "ash/wm/mru_window_tracker.h"
+#include "ash/wm/window_state.h"
+#include "base/command_line.h"
+#include "ui/display/manager/display_manager.h"
+#include "ui/display/screen.h"
+
+namespace ash {
+
+namespace {
+
+display::DisplayManager* GetDisplayManager() {
+  return Shell::Get()->display_manager();
+}
+
+MruWindowTracker::WindowList GetWindowList() {
+  return Shell::Get()->mru_window_tracker()->BuildWindowForCycleList();
+}
+
+// Returns true when window cycle list can be processed to perform save/restore
+// operations on observing display changes.
+bool ShouldProcessWindowList() {
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kAshEnablePersistentWindowBounds)) {
+    return false;
+  }
+
+  // Window cycle list exists in active user session only.
+  if (Shell::Get()->session_controller()->IsUserSessionBlocked())
+    return false;
+
+  // TODO(warx): Decide on the correct behavior involving mixed mirror mode.
+  if (GetDisplayManager()->IsInMirrorMode())
+    return false;
+
+  return true;
+}
+
+void MaybeRestorePersistentWindowBounds() {
+  if (!ShouldProcessWindowList())
+    return;
+
+  display::Screen* screen = display::Screen::GetScreen();
+  for (auto* window : GetWindowList()) {
+    wm::WindowState* window_state = wm::GetWindowState(window);
+    if (!window_state->persistent_window_info())
+      continue;
+    const auto& persistent_window_info =
+        *window_state->persistent_window_info();
+    const int64_t persistent_display_id = persistent_window_info.display_id;
+    if (persistent_display_id == screen->GetDisplayNearestWindow(window).id())
+      continue;
+    const auto& display =
+        GetDisplayManager()->GetDisplayForId(persistent_display_id);
+    if (!display.is_valid())
+      continue;
+
+    // Update |persistent_window_bounds| based on |persistent_display_bounds|'s
+    // position change. This ensures that |persistent_window_bounds| is
+    // associated with the right target display.
+    gfx::Rect persistent_window_bounds =
+        persistent_window_info.window_bounds_in_screen;
+    const auto& persistent_display_bounds =
+        persistent_window_info.display_bounds_in_screen;
+    // It is possible to have display size change, such as changing cable, bad
+    // cable signal etc., but it should be rare.
+    DCHECK(display.bounds().size() == persistent_display_bounds.size());
+    const gfx::Vector2d offset = display.bounds().OffsetFromOrigin() -
+                                 persistent_display_bounds.OffsetFromOrigin();
+    persistent_window_bounds.Offset(offset);
+
+    window->SetBoundsInScreen(persistent_window_bounds, display);
+    // Reset persistent window info everytime the window bounds have restored.
+    window_state->ResetPersistentWindowInfo();
+  }
+}
+
+}  // namespace
+
+PersistentWindowController::PersistentWindowController() {
+  display::Screen::GetScreen()->AddObserver(this);
+  Shell::Get()->session_controller()->AddObserver(this);
+  Shell::Get()->window_tree_host_manager()->AddObserver(this);
+}
+
+PersistentWindowController::~PersistentWindowController() {
+  Shell::Get()->window_tree_host_manager()->RemoveObserver(this);
+  Shell::Get()->session_controller()->RemoveObserver(this);
+  display::Screen::GetScreen()->RemoveObserver(this);
+}
+
+void PersistentWindowController::OnWillProcessDisplayChanges() {
+  if (!ShouldProcessWindowList())
+    return;
+
+  for (auto* window : GetWindowList()) {
+    wm::WindowState* window_state = wm::GetWindowState(window);
+    // This implies that we keep the first persistent info until they're valid
+    // to restore, or until they're cleared by user-invoked bounds change.
+    if (window_state->persistent_window_info())
+      continue;
+    window_state->SetPersistentWindowInfo(PersistentWindowInfo(window));
+  }
+}
+
+void PersistentWindowController::OnSessionStateChanged(
+    session_manager::SessionState state) {
+  MaybeRestorePersistentWindowBounds();
+}
+
+void PersistentWindowController::OnDisplayConfigurationChanged() {
+  MaybeRestorePersistentWindowBounds();
+}
+
+}  // namespace ash

ash/display/persistent_window_controller.h

+// Copyright 2018 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.
+
+#ifndef ASH_DISPLAY_PERSISTENT_WINDOW_CONTROLLER_H_
+#define ASH_DISPLAY_PERSISTENT_WINDOW_CONTROLLER_H_
+
+#include "ash/ash_export.h"
+#include "ash/display/window_tree_host_manager.h"
+#include "ash/session/session_observer.h"
+#include "base/macros.h"
+#include "ui/display/display_observer.h"
+
+namespace ash {
+
+// Observes display changes and saves/restores window bounds persistently in
+// multi-displays scenario.
+class ASH_EXPORT PersistentWindowController
+    : public display::DisplayObserver,
+      public SessionObserver,
+      public WindowTreeHostManager::Observer {
+ public:
+  PersistentWindowController();
+  ~PersistentWindowController() override;
+
+ private:
+  // display::DisplayObserver:
+  void OnWillProcessDisplayChanges() override;
+
+  // SessionObserver:
+  void OnSessionStateChanged(session_manager::SessionState state) override;
+
+  // WindowTreeHostManager::Observer:
+  void OnDisplayConfigurationChanged() override;
+
+  DISALLOW_COPY_AND_ASSIGN(PersistentWindowController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_DISPLAY_PERSISTENT_WINDOW_CONTROLLER_H_

ash/display/persistent_window_controller_unittest.cc

+// Copyright 2018 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/persistent_window_controller.h"
+
+#include "ash/display/display_move_window_util.h"
+#include "ash/display/window_tree_host_manager.h"
+#include "ash/public/cpp/ash_switches.h"
+#include "ash/session/test_session_controller_client.h"
+#include "ash/shell.h"
+#include "ash/test/ash_test_base.h"
+#include "ash/wm/window_state.h"
+#include "ash/wm/window_util.h"
+#include "base/command_line.h"
+
+using session_manager::SessionState;
+
+namespace ash {
+
+class PersistentWindowControllerTest : public AshTestBase {
+ protected:
+  PersistentWindowControllerTest() = default;
+  ~PersistentWindowControllerTest() override = default;
+
+  // AshTestBase:
+  void SetUp() override {
+    base::CommandLine::ForCurrentProcess()->AppendSwitch(
+        switches::kAshEnableDisplayMoveWindowAccels);
+    base::CommandLine::ForCurrentProcess()->AppendSwitch(
+        switches::kAshEnablePersistentWindowBounds);
+    AshTestBase::SetUp();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PersistentWindowControllerTest);
+};
+
+TEST_F(PersistentWindowControllerTest, DisconnectDisplay) {
+  UpdateDisplay("0+0-500x500,0+501-500x500");
+
+  aura::Window* w1 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(200, 0, 100, 200));
+  aura::Window* w2 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(501, 0, 200, 100));
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  const int64_t primary_id = WindowTreeHostManager::GetPrimaryDisplayId();
+  const int64_t secondary_id = display_manager()->GetSecondaryDisplay().id();
+
+  display::ManagedDisplayInfo primary_info =
+      display_manager()->GetDisplayInfo(primary_id);
+  display::ManagedDisplayInfo secondary_info =
+      display_manager()->GetDisplayInfo(secondary_id);
+
+  // Disconnects secondary display.
+  std::vector<display::ManagedDisplayInfo> display_info_list;
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Reconnects secondary display.
+  display_info_list.push_back(secondary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Disconnects primary display.
+  display_info_list.clear();
+  display_info_list.push_back(secondary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Reconnects primary display.
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Disconnects secondary display.
+  display_info_list.clear();
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+
+  // A third id which is different from primary and secondary.
+  const int64_t third_id = secondary_id + 1;
+  display::ManagedDisplayInfo third_info =
+      display::CreateDisplayInfo(third_id, gfx::Rect(0, 501, 500, 500));
+  // Connects another secondary display with |third_id|.
+  display_info_list.push_back(third_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+  // Connects secondary display with |secondary_id|.
+  display_info_list.clear();
+  display_info_list.push_back(primary_info);
+  display_info_list.push_back(secondary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Disconnects secondary display.
+  display_info_list.clear();
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+
+  // Sets |w2|'s bounds changed by user and then reconnects secondary display.
+  wm::WindowState* w2_state = wm::GetWindowState(w2);
+  w2_state->set_bounds_changed_by_user(true);
+  display_info_list.push_back(secondary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+}
+
+TEST_F(PersistentWindowControllerTest, ThreeDisplays) {
+  UpdateDisplay("0+0-500x500,0+501-500x500,0+1002-500x500");
+
+  aura::Window* w1 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(200, 0, 100, 200));
+  aura::Window* w2 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(501, 0, 200, 100));
+  aura::Window* w3 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(1002, 0, 400, 200));
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1002, 0, 400, 200), w3->GetBoundsInScreen());
+
+  const int64_t primary_id = display_manager()->GetDisplayAt(0).id();
+  const int64_t second_id = display_manager()->GetDisplayAt(1).id();
+  const int64_t third_id = display_manager()->GetDisplayAt(2).id();
+
+  display::ManagedDisplayInfo primary_info =
+      display_manager()->GetDisplayInfo(primary_id);
+  display::ManagedDisplayInfo second_info =
+      display_manager()->GetDisplayInfo(second_id);
+  display::ManagedDisplayInfo third_info =
+      display_manager()->GetDisplayInfo(third_id);
+
+  // Disconnects third display.
+  std::vector<display::ManagedDisplayInfo> display_info_list;
+  display_info_list.push_back(primary_info);
+  display_info_list.push_back(second_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(2, 0, 400, 200), w3->GetBoundsInScreen());
+
+  // Disconnects second display.
+  display_info_list.clear();
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(2, 0, 400, 200), w3->GetBoundsInScreen());
+
+  // Reconnects third display.
+  display_info_list.push_back(third_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(502, 0, 400, 200), w3->GetBoundsInScreen());
+
+  // Reconnects second display.
+  display_info_list.push_back(second_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1002, 0, 400, 200), w3->GetBoundsInScreen());
+
+  // Disconnects both external displays.
+  display_info_list.clear();
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(2, 0, 400, 200), w3->GetBoundsInScreen());
+
+  // Reconnects second display.
+  display_info_list.push_back(second_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(2, 0, 400, 200), w3->GetBoundsInScreen());
+
+  // Reconnects third display.
+  display_info_list.push_back(third_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1002, 0, 400, 200), w3->GetBoundsInScreen());
+}
+
+TEST_F(PersistentWindowControllerTest, EnableAndDisableMirrorMode) {
+  UpdateDisplay("0+0-500x500,0+501-500x500");
+
+  aura::Window* w1 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(200, 0, 100, 200));
+  aura::Window* w2 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(501, 0, 200, 100));
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Enables mirror mode.
+  display_manager()->SetMirrorMode(display::MirrorMode::kNormal, base::nullopt);
+  EXPECT_TRUE(display_manager()->IsInMirrorMode());
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+  // Disables mirror mode.
+  display_manager()->SetMirrorMode(display::MirrorMode::kOff, base::nullopt);
+  EXPECT_FALSE(display_manager()->IsInMirrorMode());
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+}
+
+TEST_F(PersistentWindowControllerTest, WindowMovedByAccel) {
+  UpdateDisplay("0+0-500x500,0+501-500x500");
+
+  aura::Window* w1 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(200, 0, 100, 200));
+  aura::Window* w2 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(501, 0, 200, 100));
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  const int64_t primary_id = WindowTreeHostManager::GetPrimaryDisplayId();
+  const int64_t secondary_id = display_manager()->GetSecondaryDisplay().id();
+
+  display::ManagedDisplayInfo primary_info =
+      display_manager()->GetDisplayInfo(primary_id);
+  display::ManagedDisplayInfo secondary_info =
+      display_manager()->GetDisplayInfo(secondary_id);
+
+  // Disconnects secondary display.
+  std::vector<display::ManagedDisplayInfo> display_info_list;
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Reconnects secondary display.
+  display_info_list.push_back(secondary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Moves |w2| to primary display by accelerators after we reset the persistent
+  // window info. It should be able to save persistent window info again on next
+  // display change.
+  wm::ActivateWindow(w2);
+  HandleMoveActiveWindowToDisplay(DisplayMoveWindowDirection::kLeft);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Disconnects secondary display.
+  display_info_list.clear();
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Reconnects secondary display.
+  display_info_list.push_back(secondary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+}
+
+TEST_F(PersistentWindowControllerTest, ReconnectOnLockScreen) {
+  UpdateDisplay("0+0-500x500,0+501-500x500");
+
+  aura::Window* w1 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(200, 0, 100, 200));
+  aura::Window* w2 =
+      CreateTestWindowInShellWithBounds(gfx::Rect(501, 0, 200, 100));
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+
+  const int64_t primary_id = WindowTreeHostManager::GetPrimaryDisplayId();
+  const int64_t secondary_id = display_manager()->GetSecondaryDisplay().id();
+
+  display::ManagedDisplayInfo primary_info =
+      display_manager()->GetDisplayInfo(primary_id);
+  display::ManagedDisplayInfo secondary_info =
+      display_manager()->GetDisplayInfo(secondary_id);
+
+  // Disconnects secondary display.
+  std::vector<display::ManagedDisplayInfo> display_info_list;
+  display_info_list.push_back(primary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Spin a run loop to ensure shelf is deleted. https://crbug.com/810807.
+  base::RunLoop().RunUntilIdle();
+
+  // Enters locked session state and reconnects secondary display.
+  GetSessionControllerClient()->SetSessionState(SessionState::LOCKED);
+  display_info_list.push_back(secondary_info);
+  display_manager()->OnNativeDisplaysChanged(display_info_list);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(1, 0, 200, 100), w2->GetBoundsInScreen());
+
+  // Unlocks and checks that |w2| is restored.
+  GetSessionControllerClient()->SetSessionState(SessionState::ACTIVE);
+  EXPECT_EQ(gfx::Rect(200, 0, 100, 200), w1->GetBoundsInScreen());
+  EXPECT_EQ(gfx::Rect(501, 0, 200, 100), w2->GetBoundsInScreen());
+}
+
+}  // namespace ash

ash/display/persistent_window_info.cc

+// Copyright 2018 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/persistent_window_info.h"
+
+#include "ui/aura/window.h"
+#include "ui/display/display.h"
+#include "ui/display/screen.h"
+
+namespace ash {
+
+PersistentWindowInfo::PersistentWindowInfo(aura::Window* window) {
+  const auto& display =
+      display::Screen::GetScreen()->GetDisplayNearestWindow(window);
+  window_bounds_in_screen = window->GetBoundsInScreen();
+  display_id = display.id();
+  display_bounds_in_screen = display.bounds();
+}
+
+PersistentWindowInfo::~PersistentWindowInfo() = default;
+
+}  // namespace ash

ash/display/persistent_window_info.h

+// Copyright 2018 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.
+
+#ifndef ASH_DISPLAY_PERSISTENT_WINDOW_INFO_H_
+#define ASH_DISPLAY_PERSISTENT_WINDOW_INFO_H_
+
+#include <stdint.h>
+
+#include "ash/ash_export.h"
+#include "ui/gfx/geometry/rect.h"
+
+namespace aura {
+class Window;
+}  // namespace aura
+
+namespace ash {
+
+// Describes the information that each window needs to carry for persistent
+// window placement in multi-displays scenario.
+struct ASH_EXPORT PersistentWindowInfo {
+  explicit PersistentWindowInfo(aura::Window* window);
+  ~PersistentWindowInfo();
+
+  // Persistent window bounds in screen coordinates.
+  gfx::Rect window_bounds_in_screen;
+
+  // Indicates the display to restore to when available.
+  int64_t display_id;
+
+  // Indicates last display bounds for |display_id| in screen coordinates.
+  gfx::Rect display_bounds_in_screen;
+};
+
+}  // namespace ash
+
+#endif  // ASH_DISPLAY_PERSISTENT_WINDOW_INFO_H_

ash/shell.cc

@@ -28,6 +28,7 @@
 #include "ash/display/display_shutdown_observer.h"
 #include "ash/display/event_transformation_handler.h"
 #include "ash/display/mouse_cursor_event_filter.h"
+#include "ash/display/persistent_window_controller.h"
 #include "ash/display/projecting_observer_chromeos.h"
 #include "ash/display/resolution_notification_controller.h"
 #include "ash/display/screen_ash.h"
@@ -726,6 +727,8 @@ Shell::~Shell() {
   // Controllers who have WindowObserver added must be deleted
   // before |window_tree_host_manager_| is deleted.
 
+  persistent_window_controller_.reset();
+
   // VideoActivityNotifier must be deleted before |video_detector_| is
   // deleted because it's observing video activity through
   // VideoDetector::Observer interface.
@@ -1166,6 +1169,8 @@ void Shell::InitializeDisplayManager() {
           display_manager_.get(), window_tree_host_manager_.get());
   display_configurator_->Init(shell_port_->CreateNativeDisplayDelegate(),
                               false);
+  persistent_window_controller_ =
+      std::make_unique<PersistentWindowController>();
 
   projecting_observer_ =
       std::make_unique<ProjectingObserver>(display_configurator_.get());

ash/shell.h

@@ -125,6 +125,7 @@ class NoteTakingController;
 class OverlayEventFilter;
 class PartialMagnificationController;
 class PeripheralBatteryNotifier;
+class PersistentWindowController;
 class PowerButtonController;
 class PowerEventObserver;
 class ProjectingObserver;
@@ -696,6 +697,7 @@ class ASH_EXPORT Shell : public SessionObserver,
   std::unique_ptr<ui::UserActivityDetector> user_activity_detector_;
   std::unique_ptr<VideoDetector> video_detector_;
   std::unique_ptr<WindowTreeHostManager> window_tree_host_manager_;
+  std::unique_ptr<PersistentWindowController> persistent_window_controller_;
   std::unique_ptr<HighContrastController> high_contrast_controller_;
   std::unique_ptr<MagnificationController> magnification_controller_;
   std::unique_ptr<AutoclickController> autoclick_controller_;

ash/wm/window_state.cc

@@ -385,6 +385,15 @@ void WindowState::SetPreAddedToWorkspaceWindowBounds(const gfx::Rect& bounds) {
   pre_added_to_workspace_window_bounds_ = base::make_optional(bounds);
 }
 
+void WindowState::SetPersistentWindowInfo(
+    const PersistentWindowInfo& persistent_window_info) {
+  persistent_window_info_ = base::make_optional(persistent_window_info);
+}
+
+void WindowState::ResetPersistentWindowInfo() {
+  persistent_window_info_.reset();
+}
+
 void WindowState::AddObserver(WindowStateObserver* observer) {
   observer_list_.AddObserver(observer);
 }
@@ -432,6 +441,7 @@ void WindowState::set_bounds_changed_by_user(bool bounds_changed_by_user) {
   if (bounds_changed_by_user) {
     pre_auto_manage_window_bounds_.reset();
     pre_added_to_workspace_window_bounds_.reset();
+    persistent_window_info_.reset();
   }
 }
 

ash/wm/window_state.h

@@ -8,6 +8,7 @@
 #include <memory>
 
 #include "ash/ash_export.h"
+#include "ash/display/persistent_window_info.h"
 #include "ash/public/interfaces/window_state_type.mojom.h"
 #include "ash/wm/drag_details.h"
 #include "base/gtest_prod_util.h"
@@ -238,17 +239,26 @@ class ASH_EXPORT WindowState : public aura::WindowObserver {
 
   // Gets/Sets the bounds of the window before it was moved by the auto window
   // management. As long as it was not auto-managed, it will return NULL.
-  base::Optional<gfx::Rect> pre_auto_manage_window_bounds() const {
+  const base::Optional<gfx::Rect> pre_auto_manage_window_bounds() {
     return pre_auto_manage_window_bounds_;
   }
   void SetPreAutoManageWindowBounds(const gfx::Rect& bounds);
 
   // Gets/Sets the property that is used on window added to workspace event.
-  base::Optional<gfx::Rect> pre_added_to_workspace_window_bounds() const {
+  const base::Optional<gfx::Rect> pre_added_to_workspace_window_bounds() {
     return pre_added_to_workspace_window_bounds_;
   }
   void SetPreAddedToWorkspaceWindowBounds(const gfx::Rect& bounds);
 
+  // Gets/Sets the persistent window info that is used on restoring persistent
+  // window bounds in multi-displays scenario.
+  const base::Optional<PersistentWindowInfo> persistent_window_info() {
+    return persistent_window_info_;
+  }
+  void SetPersistentWindowInfo(
+      const PersistentWindowInfo& persistent_window_info);
+  void ResetPersistentWindowInfo();
+
   // Layout related properties
 
   void AddObserver(WindowStateObserver* observer);
@@ -426,6 +436,11 @@ class ASH_EXPORT WindowState : public aura::WindowObserver {
   // nullptr, and window is removing from a workspace.
   base::Optional<gfx::Rect> pre_added_to_workspace_window_bounds_;
 
+  // A property to remember the persistent window info used in multi-displays
+  // scenario to attempt to restore windows to their original bounds when
+  // displays are restored to their previous states.
+  base::Optional<PersistentWindowInfo> persistent_window_info_;
+
   base::ObserverList<WindowStateObserver> observer_list_;
 
   // True to ignore a property change event to avoid reentrance in