Add rudimentary mash shelf functionality.

Add UserWindow[Controller|Observer] interfaces and impls.
Move shelf code from mojo:system_ui to mojo:shelf.
Add views_examples and task_viewer buttons to the shelf.
Show buttons for open user windows; they focus on press.
Cleanup mash deps tree (move data_deps from all to shell).

BUG=557406
TEST=mojo:mash_shell shelf has rudimentary functionality.
R=sky@chromium.org

Review URL: https://codereview.chromium.org/1576683002

Cr-Commit-Position: refs/heads/master@{#369330}

18 files changed, 422 insertions, 112 deletions

diff --git a/mash/BUILD.gn b/mash/BUILD.gn
index 8550b7c..37db36d 100644
--- a/mash/BUILD.gn
+++ b/mash/BUILD.gn
@@ -11,11 +11,8 @@ group("all") {
   deps = [
     ":tests",
     "//mash/example",
-    "//mash/quick_launch",
     "//mash/shell",
     "//mash/task_viewer",
-    "//mash/wallpaper",
-    "//mash/wm",
   ]
 }
 
diff --git a/mash/system_ui/BUILD.gn b/mash/shelf/BUILD.gn
index 6252901..8c316a7 100644
--- a/mash/system_ui/BUILD.gn
+++ b/mash/shelf/BUILD.gn
@@ -6,11 +6,13 @@ import("//build/config/ui.gni")
 import("//mojo/public/mojo_application.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
-mojo_native_application("system_ui") {
+mojo_native_application("shelf") {
   sources = [
     "main.cc",
-    "system_ui.cc",
-    "system_ui.h",
+    "shelf_application.cc",
+    "shelf_application.h",
+    "shelf_view.cc",
+    "shelf_view.h",
   ]
 
   deps = [
diff --git a/mash/system_ui/main.cc b/mash/shelf/main.cc
index 0c5832b..636e0e0 100644
--- a/mash/system_ui/main.cc
+++ b/mash/shelf/main.cc
@@ -2,11 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "mash/system_ui/system_ui.h"
+#include "mash/shelf/shelf_application.h"
 #include "mojo/public/c/system/main.h"
 #include "mojo/shell/public/cpp/application_runner.h"
 
 MojoResult MojoMain(MojoHandle shell_handle) {
-  mojo::ApplicationRunner runner(new mash::system_ui::SystemUI);
+  mojo::ApplicationRunner runner(new mash::shelf::ShelfApplication);
   return runner.Run(shell_handle);
 }
diff --git a/mash/shelf/shelf_application.cc b/mash/shelf/shelf_application.cc
new file mode 100644
index 0000000..4656978
--- /dev/null
+++ b/mash/shelf/shelf_application.cc
@@ -0,0 +1,53 @@
+// Copyright 2015 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 "mash/shelf/shelf_application.h"
+
+#include <stdint.h>
+
+#include "components/mus/public/cpp/property_type_converters.h"
+#include "mash/shelf/shelf_view.h"
+#include "mash/wm/public/interfaces/container.mojom.h"
+#include "mojo/shell/public/cpp/application_impl.h"
+#include "ui/views/mus/aura_init.h"
+#include "ui/views/mus/native_widget_mus.h"
+#include "ui/views/mus/window_manager_connection.h"
+
+namespace mash {
+namespace shelf {
+
+ShelfApplication::ShelfApplication() {}
+
+ShelfApplication::~ShelfApplication() {}
+
+void ShelfApplication::Initialize(mojo::ApplicationImpl* app) {
+  tracing_.Initialize(app);
+
+  aura_init_.reset(new views::AuraInit(app, "views_mus_resources.pak"));
+  views::WindowManagerConnection::Create(app);
+
+  views::Widget* widget = new views::Widget;
+  views::Widget::InitParams params(
+      views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
+  params.delegate = new ShelfView(app);
+
+  std::map<std::string, std::vector<uint8_t>> properties;
+  properties[mash::wm::mojom::kWindowContainer_Property] =
+      mojo::TypeConverter<const std::vector<uint8_t>, int32_t>::Convert(
+          mash::wm::mojom::CONTAINER_USER_SHELF);
+  mus::Window* window =
+      views::WindowManagerConnection::Get()->NewWindow(properties);
+  params.native_widget = new views::NativeWidgetMus(
+      widget, app->shell(), window, mus::mojom::SURFACE_TYPE_DEFAULT);
+  widget->Init(params);
+  widget->Show();
+}
+
+bool ShelfApplication::ConfigureIncomingConnection(
+    mojo::ApplicationConnection* connection) {
+  return true;
+}
+
+}  // namespace shelf
+}  // namespace mash
diff --git a/mash/system_ui/system_ui.h b/mash/shelf/shelf_application.h
index 86bfb22..901bdfa 100644
--- a/mash/system_ui/system_ui.h
+++ b/mash/shelf/shelf_application.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef MASH_SYSTEM_UI_SYSTEM_UI_H_
-#define MASH_SYSTEM_UI_SYSTEM_UI_H_
+#ifndef MASH_SHELF_SHELF_APPLICATION_H_
+#define MASH_SHELF_SHELF_APPLICATION_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
@@ -15,12 +15,12 @@ class AuraInit;
 }
 
 namespace mash {
-namespace system_ui {
+namespace shelf {
 
-class SystemUI : public mojo::ApplicationDelegate {
+class ShelfApplication : public mojo::ApplicationDelegate {
  public:
-  SystemUI();
-  ~SystemUI() override;
+  ShelfApplication();
+  ~ShelfApplication() override;
 
  private:
   // mojo::ApplicationDelegate:
@@ -32,10 +32,10 @@ class SystemUI : public mojo::ApplicationDelegate {
 
   scoped_ptr<views::AuraInit> aura_init_;
 
-  DISALLOW_COPY_AND_ASSIGN(SystemUI);
+  DISALLOW_COPY_AND_ASSIGN(ShelfApplication);
 };
 
-}  // namespace system_ui
+}  // namespace shelf
 }  // namespace mash
 
-#endif  // MASH_SYSTEM_UI_SYSTEM_UI_H_
+#endif  // MASH_SHELF_SHELF_APPLICATION_H_
diff --git a/mash/shelf/shelf_view.cc b/mash/shelf/shelf_view.cc
new file mode 100644
index 0000000..6af2a5a
--- /dev/null
+++ b/mash/shelf/shelf_view.cc
@@ -0,0 +1,98 @@
+// Copyright 2015 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 "mash/shelf/shelf_view.h"
+
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
+#include "mojo/shell/public/cpp/application_impl.h"
+#include "ui/gfx/canvas.h"
+#include "ui/views/controls/button/label_button.h"
+#include "ui/views/layout/box_layout.h"
+
+namespace mash {
+namespace shelf {
+
+enum ShelfButtonID {
+  SHELF_BUTTON_VIEWS_EXAMPLES,
+  SHELF_BUTTON_TASK_VIEWER,
+};
+
+ShelfView::ShelfView(mojo::ApplicationImpl* app) : app_(app), binding_(this) {
+  app->ConnectToService("mojo:desktop_wm", &user_window_controller_);
+
+  mash::wm::mojom::UserWindowObserverPtr observer;
+  mojo::InterfaceRequest<mash::wm::mojom::UserWindowObserver> request =
+      mojo::GetProxy(&observer);
+  user_window_controller_->AddUserWindowObserver(std::move(observer));
+  binding_.Bind(std::move(request));
+
+  SetLayoutManager(
+      new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, 0));
+
+  views::LabelButton* views_examples =
+      new views::LabelButton(this, base::ASCIIToUTF16("Views Examples"));
+  views_examples->set_tag(SHELF_BUTTON_VIEWS_EXAMPLES);
+  AddChildView(views_examples);
+
+  views::LabelButton* task_viewer =
+      new views::LabelButton(this, base::ASCIIToUTF16("Task Viewer"));
+  task_viewer->set_tag(SHELF_BUTTON_TASK_VIEWER);
+  AddChildView(task_viewer);
+}
+
+ShelfView::~ShelfView() {}
+
+void ShelfView::OnPaint(gfx::Canvas* canvas) {
+  canvas->FillRect(GetLocalBounds(), SK_ColorYELLOW);
+  views::View::OnPaint(canvas);
+}
+
+gfx::Size ShelfView::GetPreferredSize() const {
+  return gfx::Size(1, 48);
+}
+
+views::View* ShelfView::GetContentsView() {
+  return this;
+}
+
+void ShelfView::ButtonPressed(views::Button* sender, const ui::Event& event) {
+  if (sender->tag() == SHELF_BUTTON_VIEWS_EXAMPLES)
+    app_->ConnectToApplication("mojo:views_examples");
+  else if (sender->tag() == SHELF_BUTTON_TASK_VIEWER)
+    app_->ConnectToApplication("mojo:task_viewer");
+  else
+    user_window_controller_->FocusUserWindow(sender->tag());
+}
+
+void ShelfView::OnUserWindowObserverAdded(mojo::Array<uint32_t> window_ids) {
+  for (size_t i = 0; i < window_ids.size(); ++i)
+    OnUserWindowAdded(window_ids[i]);
+}
+
+void ShelfView::OnUserWindowAdded(uint32_t window_id) {
+  // TODO(msw): Get the actual window title and icon.
+  views::LabelButton* open_window_button = new views::LabelButton(
+      this, base::ASCIIToUTF16(base::StringPrintf("Window %d", window_id)));
+  open_window_button->set_tag(window_id);
+  open_window_buttons_.push_back(open_window_button);
+  AddChildView(open_window_button);
+  Layout();
+  SchedulePaint();
+}
+
+void ShelfView::OnUserWindowRemoved(uint32_t window_id) {
+  for (size_t i = 0; i < open_window_buttons_.size(); ++i) {
+    if (static_cast<uint32_t>(open_window_buttons_[i]->tag()) == window_id) {
+      views::LabelButton* button = open_window_buttons_[i];
+      open_window_buttons_.erase(open_window_buttons_.begin() + i);
+      RemoveChildView(button);
+      delete button;
+      return;
+    }
+  }
+}
+
+}  // namespace shelf
+}  // namespace mash
diff --git a/mash/shelf/shelf_view.h b/mash/shelf/shelf_view.h
new file mode 100644
index 0000000..f631dbd
--- /dev/null
+++ b/mash/shelf/shelf_view.h
@@ -0,0 +1,62 @@
+// Copyright 2015 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 MASH_SHELF_SHELF_VIEW_H_
+#define MASH_SHELF_SHELF_VIEW_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "mash/wm/public/interfaces/user_window_controller.mojom.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "ui/views/controls/button/button.h"
+#include "ui/views/widget/widget_delegate.h"
+
+namespace mojo {
+class ApplicationImpl;
+}
+
+namespace views {
+class LabelButton;
+}
+
+namespace mash {
+namespace shelf {
+
+// A rudimentary mash shelf, used to build up the required wm interfaces.
+class ShelfView : public views::WidgetDelegateView,
+                  public views::ButtonListener,
+                  public mash::wm::mojom::UserWindowObserver {
+ public:
+  explicit ShelfView(mojo::ApplicationImpl* app);
+  ~ShelfView() override;
+
+ private:
+  // Overridden from views::View:
+  void OnPaint(gfx::Canvas* canvas) override;
+  gfx::Size GetPreferredSize() const override;
+
+  // Overridden from views::WidgetDelegate:
+  views::View* GetContentsView() override;
+
+  // Overridden from views::ButtonListener:
+  void ButtonPressed(views::Button* sender, const ui::Event& event) override;
+
+  // Overridden from mash::wm::mojom::UserWindowObserver:
+  void OnUserWindowObserverAdded(mojo::Array<uint32_t> window_ids) override;
+  void OnUserWindowAdded(uint32_t window_id) override;
+  void OnUserWindowRemoved(uint32_t window_id) override;
+
+  mojo::ApplicationImpl* app_;
+  std::vector<views::LabelButton*> open_window_buttons_;
+  mash::wm::mojom::UserWindowControllerPtr user_window_controller_;
+  mojo::Binding<mash::wm::mojom::UserWindowObserver> binding_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShelfView);
+};
+
+}  // namespace shelf
+}  // namespace mash
+
+#endif  // MASH_SHELF_SHELF_VIEW_H_
diff --git a/mash/shell/BUILD.gn b/mash/shell/BUILD.gn
index 2a4b763..25487bd 100644
--- a/mash/shell/BUILD.gn
+++ b/mash/shell/BUILD.gn
@@ -25,7 +25,9 @@ mojo_native_application("shell") {
 
   data_deps = [
     "//mash/browser_driver",
-    "//mash/system_ui",
+    "//mash/quick_launch",
+    "//mash/shelf",
+    "//mash/wallpaper",
     "//mash/wm",
   ]
 }
diff --git a/mash/shell/shell_application_delegate.cc b/mash/shell/shell_application_delegate.cc
index 11f5cb7..6672295 100644
--- a/mash/shell/shell_application_delegate.cc
+++ b/mash/shell/shell_application_delegate.cc
@@ -20,7 +20,7 @@ void ShellApplicationDelegate::Initialize(mojo::ApplicationImpl* app) {
   StartBrowserDriver();
   StartWindowManager();
   StartWallpaper();
-  StartSystemUI();
+  StartShelf();
   StartQuickLaunch();
 }
 
@@ -42,9 +42,9 @@ void ShellApplicationDelegate::StartWallpaper() {
                                      base::Unretained(this)));
 }
 
-void ShellApplicationDelegate::StartSystemUI() {
-  StartRestartableService("mojo:system_ui",
-                          base::Bind(&ShellApplicationDelegate::StartSystemUI,
+void ShellApplicationDelegate::StartShelf() {
+  StartRestartableService("mojo:shelf",
+                          base::Bind(&ShellApplicationDelegate::StartShelf,
                                      base::Unretained(this)));
 }
 
diff --git a/mash/shell/shell_application_delegate.h b/mash/shell/shell_application_delegate.h
index cca181d..c2230dd 100644
--- a/mash/shell/shell_application_delegate.h
+++ b/mash/shell/shell_application_delegate.h
@@ -32,7 +32,7 @@ class ShellApplicationDelegate : public mojo::ApplicationDelegate {
 
   void StartWindowManager();
   void StartWallpaper();
-  void StartSystemUI();
+  void StartShelf();
   void StartBrowserDriver();
   void StartQuickLaunch();
 
diff --git a/mash/system_ui/system_ui.cc b/mash/system_ui/system_ui.cc
deleted file mode 100644
index 6761365..0000000
--- a/mash/system_ui/system_ui.cc
+++ /dev/null
@@ -1,82 +0,0 @@
-// Copyright 2015 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 "mash/system_ui/system_ui.h"
-
-#include <stdint.h>
-
-#include "base/macros.h"
-#include "components/mus/public/cpp/property_type_converters.h"
-#include "mash/wm/public/interfaces/container.mojom.h"
-#include "mojo/shell/public/cpp/application_connection.h"
-#include "mojo/shell/public/cpp/application_impl.h"
-#include "ui/gfx/canvas.h"
-#include "ui/views/mus/aura_init.h"
-#include "ui/views/mus/native_widget_mus.h"
-#include "ui/views/mus/window_manager_connection.h"
-#include "ui/views/widget/widget_delegate.h"
-
-namespace mash {
-namespace system_ui {
-namespace {
-
-class Shelf : public views::WidgetDelegateView {
- public:
-  static void Create(mojo::Shell* shell) {
-    views::Widget* widget = new views::Widget;
-    views::Widget::InitParams params(
-        views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
-    params.delegate = new Shelf;
-
-    std::map<std::string, std::vector<uint8_t>> properties;
-    properties[mash::wm::mojom::kWindowContainer_Property] =
-        mojo::TypeConverter<const std::vector<uint8_t>, int32_t>::Convert(
-            mash::wm::mojom::CONTAINER_USER_SHELF);
-    mus::Window* window =
-        views::WindowManagerConnection::Get()->NewWindow(properties);
-    params.native_widget = new views::NativeWidgetMus(
-        widget, shell, window, mus::mojom::SURFACE_TYPE_DEFAULT);
-    widget->Init(params);
-    widget->Show();
-  }
-
- private:
-  Shelf() {}
-  ~Shelf() override {}
-
-  // Overridden from views::View:
-  void OnPaint(gfx::Canvas* canvas) override {
-    canvas->FillRect(GetLocalBounds(), SK_ColorYELLOW);
-  }
-  gfx::Size GetPreferredSize() const override { return gfx::Size(1, 48); }
-
-  // Overridden from views::WidgetDelegate:
-  views::View* GetContentsView() override { return this; }
-
-  DISALLOW_COPY_AND_ASSIGN(Shelf);
-};
-
-}  // namespace
-
-SystemUI::SystemUI() {}
-
-SystemUI::~SystemUI() {
-}
-
-void SystemUI::Initialize(mojo::ApplicationImpl* app) {
-  tracing_.Initialize(app);
-
-  aura_init_.reset(new views::AuraInit(app, "views_mus_resources.pak"));
-  views::WindowManagerConnection::Create(app);
-
-  Shelf::Create(app->shell());
-}
-
-bool SystemUI::ConfigureIncomingConnection(
-    mojo::ApplicationConnection* connection) {
-  return true;
-}
-
-}  // namespace system_ui
-}  // namespace mash
diff --git a/mash/wm/BUILD.gn b/mash/wm/BUILD.gn
index 9beaa14e..e9d54ae 100644
--- a/mash/wm/BUILD.gn
+++ b/mash/wm/BUILD.gn
@@ -50,6 +50,8 @@ source_set("lib") {
     "shadow_controller.h",
     "shelf_layout.cc",
     "shelf_layout.h",
+    "user_window_controller_impl.cc",
+    "user_window_controller_impl.h",
     "window_layout.cc",
     "window_layout.h",
     "window_manager_application.cc",
diff --git a/mash/wm/public/interfaces/BUILD.gn b/mash/wm/public/interfaces/BUILD.gn
index e778f37..65b21b4 100644
--- a/mash/wm/public/interfaces/BUILD.gn
+++ b/mash/wm/public/interfaces/BUILD.gn
@@ -7,5 +7,6 @@ import("//mojo/public/tools/bindings/mojom.gni")
 mojom("interfaces") {
   sources = [
     "container.mojom",
+    "user_window_controller.mojom",
   ]
 }
diff --git a/mash/wm/public/interfaces/user_window_controller.mojom b/mash/wm/public/interfaces/user_window_controller.mojom
new file mode 100644
index 0000000..9ec33ec
--- /dev/null
+++ b/mash/wm/public/interfaces/user_window_controller.mojom
@@ -0,0 +1,22 @@
+// Copyright 2015 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.
+
+module mash.wm.mojom;
+
+// An observer of user windows within mojom::CONTAINER_USER_WINDOWS.
+// TODO(msw): Observe focus changes, title/icon changes, etc.
+interface UserWindowObserver {
+  // Called when the observer is first added to supply the initial state.
+  OnUserWindowObserverAdded(array<uint32> window_ids);
+
+  OnUserWindowAdded(uint32 window_id);
+  OnUserWindowRemoved(uint32 window_id);
+};
+
+// An interface allowing system UIs to manage the set of user windows.
+// TODO(msw): Add minimization, restoration, opening a chooser view, etc.
+interface UserWindowController {
+  AddUserWindowObserver(UserWindowObserver observer);
+  FocusUserWindow(uint32 window_id);
+};
\ No newline at end of file
diff --git a/mash/wm/user_window_controller_impl.cc b/mash/wm/user_window_controller_impl.cc
new file mode 100644
index 0000000..d4181fb
--- /dev/null
+++ b/mash/wm/user_window_controller_impl.cc
@@ -0,0 +1,63 @@
+// Copyright 2015 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 "mash/wm/user_window_controller_impl.h"
+
+#include "components/mus/public/cpp/window.h"
+#include "mash/wm/public/interfaces/container.mojom.h"
+#include "mash/wm/window_manager_application.h"
+
+namespace mash {
+namespace wm {
+
+UserWindowControllerImpl::UserWindowControllerImpl() : state_(nullptr) {}
+
+UserWindowControllerImpl::~UserWindowControllerImpl() {
+  if (state_)
+    GetUserWindowContainer()->RemoveObserver(this);
+}
+
+void UserWindowControllerImpl::Initialize(WindowManagerApplication* state) {
+  DCHECK(state);
+  DCHECK(!state_);
+  state_ = state;
+  GetUserWindowContainer()->AddObserver(this);
+}
+
+mus::Window* UserWindowControllerImpl::GetUserWindowContainer() const {
+  return state_->GetWindowForContainer(mojom::CONTAINER_USER_WINDOWS);
+}
+
+void UserWindowControllerImpl::OnTreeChanging(const TreeChangeParams& params) {
+  DCHECK(state_);
+  if (user_window_observer_) {
+    mus::Window* user_window_container = GetUserWindowContainer();
+    if (params.new_parent == user_window_container)
+      user_window_observer_->OnUserWindowAdded(params.target->id());
+    else if (params.old_parent == user_window_container)
+      user_window_observer_->OnUserWindowRemoved(params.target->id());
+  }
+}
+
+void UserWindowControllerImpl::AddUserWindowObserver(
+    mash::wm::mojom::UserWindowObserverPtr observer) {
+  // TODO(msw): Support multiple observers.
+  user_window_observer_ = std::move(observer);
+
+  const mus::Window::Children& windows = GetUserWindowContainer()->children();
+  mojo::Array<uint32_t> user_windows =
+      mojo::Array<uint32_t>::New(windows.size());
+  for (size_t i = 0; i < windows.size(); ++i)
+    user_windows[i] = windows[i]->id();
+  user_window_observer_->OnUserWindowObserverAdded(std::move(user_windows));
+}
+
+void UserWindowControllerImpl::FocusUserWindow(uint32_t window_id) {
+  mus::Window* window = GetUserWindowContainer()->GetChildById(window_id);
+  if (window)
+    window->SetFocus();
+}
+
+}  // namespace wm
+}  // namespace mash
diff --git a/mash/wm/user_window_controller_impl.h b/mash/wm/user_window_controller_impl.h
new file mode 100644
index 0000000..1737b61
--- /dev/null
+++ b/mash/wm/user_window_controller_impl.h
@@ -0,0 +1,49 @@
+// Copyright 2015 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 MASH_WM_USER_WINDOW_CONTROLLER_IMPL_H_
+#define MASH_WM_USER_WINDOW_CONTROLLER_IMPL_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "components/mus/common/types.h"
+#include "components/mus/public/cpp/window_observer.h"
+#include "mash/wm/public/interfaces/user_window_controller.mojom.h"
+
+namespace mash {
+namespace wm {
+
+class WindowManagerApplication;
+
+class UserWindowControllerImpl : public mash::wm::mojom::UserWindowController,
+                                 public mus::WindowObserver {
+ public:
+  UserWindowControllerImpl();
+  ~UserWindowControllerImpl() override;
+
+  void Initialize(WindowManagerApplication* state);
+
+ private:
+  // A helper to get the container for user windows.
+  mus::Window* GetUserWindowContainer() const;
+
+  // mus::WindowObserver:
+  void OnTreeChanging(const TreeChangeParams& params) override;
+
+  // mash::wm::mojom::UserWindowController:
+  void AddUserWindowObserver(
+      mash::wm::mojom::UserWindowObserverPtr observer) override;
+  void FocusUserWindow(uint32_t window_id) override;
+
+  WindowManagerApplication* state_;
+  mash::wm::mojom::UserWindowObserverPtr user_window_observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(UserWindowControllerImpl);
+};
+
+}  // namespace wm
+}  // namespace mash
+
+#endif  // MASH_WM_USER_WINDOW_CONTROLLER_IMPL_H_
diff --git a/mash/wm/window_manager_application.cc b/mash/wm/window_manager_application.cc
index 748bc48..4436e2e 100644
--- a/mash/wm/window_manager_application.cc
+++ b/mash/wm/window_manager_application.cc
@@ -17,6 +17,7 @@
 #include "mash/wm/background_layout.h"
 #include "mash/wm/shadow_controller.h"
 #include "mash/wm/shelf_layout.h"
+#include "mash/wm/user_window_controller_impl.h"
 #include "mash/wm/window_layout.h"
 #include "mash/wm/window_manager_impl.h"
 #include "mojo/services/tracing/public/cpp/tracing_impl.h"
@@ -79,8 +80,10 @@ void WindowManagerApplication::Initialize(mojo::ApplicationImpl* app) {
   window_manager_.reset(new WindowManagerImpl());
   // Don't bind to the WindowManager immediately. Wait for OnEmbed() first.
   mus::mojom::WindowManagerPtr window_manager;
-  requests_.push_back(new mojo::InterfaceRequest<mus::mojom::WindowManager>(
-      mojo::GetProxy(&window_manager)));
+  requests_.push_back(
+      make_scoped_ptr(new mojo::InterfaceRequest<mus::mojom::WindowManager>(
+          mojo::GetProxy(&window_manager))));
+  user_window_controller_.reset(new UserWindowControllerImpl());
   mus::mojom::WindowTreeHostClientPtr host_client;
   host_client_binding_.Bind(GetProxy(&host_client));
   mus::CreateSingleWindowTreeHost(app, std::move(host_client), this,
@@ -90,6 +93,7 @@ void WindowManagerApplication::Initialize(mojo::ApplicationImpl* app) {
 
 bool WindowManagerApplication::ConfigureIncomingConnection(
     mojo::ApplicationConnection* connection) {
+  connection->AddService<mash::wm::mojom::UserWindowController>(this);
   connection->AddService<mus::mojom::AcceleratorRegistrar>(this);
   connection->AddService<mus::mojom::WindowManager>(this);
   return true;
@@ -132,11 +136,17 @@ void WindowManagerApplication::OnEmbed(mus::Window* root) {
   aura_init_.reset(new views::AuraInit(app_, "mash_wm_resources.pak"));
   window_manager_->Initialize(this);
 
-  for (auto request : requests_)
+  for (auto& request : requests_)
     window_manager_binding_.AddBinding(window_manager_.get(),
                                        std::move(*request));
   requests_.clear();
 
+  user_window_controller_->Initialize(this);
+  for (auto& request : user_window_controller_requests_)
+    user_window_controller_binding_.AddBinding(user_window_controller_.get(),
+                                               std::move(*request));
+  user_window_controller_requests_.clear();
+
   shadow_controller_.reset(new ShadowController(root->connection()));
 }
 
@@ -149,6 +159,19 @@ void WindowManagerApplication::OnConnectionLost(
 
 void WindowManagerApplication::Create(
     mojo::ApplicationConnection* connection,
+    mojo::InterfaceRequest<mash::wm::mojom::UserWindowController> request) {
+  if (root_) {
+    user_window_controller_binding_.AddBinding(user_window_controller_.get(),
+                                               std::move(request));
+  } else {
+    user_window_controller_requests_.push_back(make_scoped_ptr(
+        new mojo::InterfaceRequest<mash::wm::mojom::UserWindowController>(
+            std::move(request))));
+  }
+}
+
+void WindowManagerApplication::Create(
+    mojo::ApplicationConnection* connection,
     mojo::InterfaceRequest<mus::mojom::AcceleratorRegistrar> request) {
   static int accelerator_registrar_count = 0;
   if (accelerator_registrar_count == std::numeric_limits<int>::max()) {
@@ -173,8 +196,9 @@ void WindowManagerApplication::Create(
     window_manager_binding_.AddBinding(window_manager_.get(),
                                        std::move(request));
   } else {
-    requests_.push_back(new mojo::InterfaceRequest<mus::mojom::WindowManager>(
-        std::move(request)));
+    requests_.push_back(
+        make_scoped_ptr(new mojo::InterfaceRequest<mus::mojom::WindowManager>(
+            std::move(request))));
   }
 }
 
diff --git a/mash/wm/window_manager_application.h b/mash/wm/window_manager_application.h
index 20593df..cf0f26c0 100644
--- a/mash/wm/window_manager_application.h
+++ b/mash/wm/window_manager_application.h
@@ -11,7 +11,6 @@
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/memory/scoped_vector.h"
 #include "components/mus/common/types.h"
 #include "components/mus/public/cpp/window_observer.h"
 #include "components/mus/public/cpp/window_tree_delegate.h"
@@ -19,6 +18,7 @@
 #include "components/mus/public/interfaces/window_manager.mojom.h"
 #include "components/mus/public/interfaces/window_tree_host.mojom.h"
 #include "mash/wm/public/interfaces/container.mojom.h"
+#include "mash/wm/public/interfaces/user_window_controller.mojom.h"
 #include "mojo/common/weak_binding_set.h"
 #include "mojo/services/tracing/public/cpp/tracing_impl.h"
 #include "mojo/shell/public/cpp/application_delegate.h"
@@ -41,6 +41,7 @@ class AcceleratorRegistrarImpl;
 class BackgroundLayout;
 class ShadowController;
 class ShelfLayout;
+class UserWindowControllerImpl;
 class WindowLayout;
 class WindowManagerImpl;
 
@@ -49,6 +50,7 @@ class WindowManagerApplication
       public mus::WindowObserver,
       public mus::mojom::WindowTreeHostClient,
       public mus::WindowTreeDelegate,
+      public mojo::InterfaceFactory<mash::wm::mojom::UserWindowController>,
       public mojo::InterfaceFactory<mus::mojom::WindowManager>,
       public mojo::InterfaceFactory<mus::mojom::AcceleratorRegistrar> {
  public:
@@ -86,6 +88,11 @@ class WindowManagerApplication
   void OnEmbed(mus::Window* root) override;
   void OnConnectionLost(mus::WindowTreeConnection* connection) override;
 
+  // InterfaceFactory<mash::wm::mojom::UserWindowController>:
+  void Create(mojo::ApplicationConnection* connection,
+              mojo::InterfaceRequest<mash::wm::mojom::UserWindowController>
+                  request) override;
+
   // InterfaceFactory<mus::mojom::AcceleratorRegistrar>:
   void Create(mojo::ApplicationConnection* connection,
               mojo::InterfaceRequest<mus::mojom::AcceleratorRegistrar> request)
@@ -120,7 +127,17 @@ class WindowManagerApplication
   // |requests_| stores any pending WindowManager interface requests.
   scoped_ptr<WindowManagerImpl> window_manager_;
   mojo::WeakBindingSet<mus::mojom::WindowManager> window_manager_binding_;
-  ScopedVector<mojo::InterfaceRequest<mus::mojom::WindowManager>> requests_;
+  std::vector<scoped_ptr<mojo::InterfaceRequest<mus::mojom::WindowManager>>>
+      requests_;
+
+  // |user_window_controller_| is created once OnEmbed() is called. Until that
+  // time |user_window_controller_requests_| stores pending interface requests.
+  scoped_ptr<UserWindowControllerImpl> user_window_controller_;
+  mojo::WeakBindingSet<mash::wm::mojom::UserWindowController>
+      user_window_controller_binding_;
+  std::vector<
+      scoped_ptr<mojo::InterfaceRequest<mash::wm::mojom::UserWindowController>>>
+      user_window_controller_requests_;
 
   scoped_ptr<BackgroundLayout> background_layout_;
   scoped_ptr<ShelfLayout> shelf_layout_;