ash: A first step for the uber tray.

As a first step, there are items to open settings, help pages, and an item to
allow [un]muting volume.

The resources have not been uploaded yet. That will be done in a separate CL to
allow this one to go through trybots etc.

This new uber-tray can be turned on at runtime using --ash-uber-tray flag.

BUG=110130
TEST=none yet. will be added when a little more fleshed out.

Review URL: https://chromiumcodereview.appspot.com/9463039

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@123799 0039d316-1c4b-4281-b951-d872f2087c98

18 files changed, 642 insertions, 0 deletions

diff --git a/ash/ash.gyp b/ash/ash.gyp
index 1919b84..5c3099d 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -110,6 +110,15 @@
         'shell_window_ids.h',
         'status_area/status_area_view.cc',
         'status_area/status_area_view.h',
+        'system/audio/tray_volume.cc',
+        'system/audio/tray_volume.h',
+        'system/settings/tray_settings.cc',
+        'system/settings/tray_settings.h',
+        'system/tray/system_tray.cc',
+        'system/tray/system_tray.h',
+        'system/tray/system_tray_delegate.h',
+        'system/tray/system_tray_item.cc',
+        'system/tray/system_tray_item.h',
         'tooltips/tooltip_controller.cc',
         'tooltips/tooltip_controller.h',
         'volume_control_delegate.h',
diff --git a/ash/ash_switches.cc b/ash/ash_switches.cc
index 69067eb..87f4c30 100644
--- a/ash/ash_switches.cc
+++ b/ash/ash_switches.cc
@@ -11,6 +11,9 @@
 namespace ash {
 namespace switches {
 
+// Use the in-progress uber system tray.
+const char kAshUberTray[] = "ash-uber-tray";
+
 // Force the "compact" window mode regardless of the value of kAuraWindowMode.
 // This can be used to override a value set in chrome://flags.
 // TODO(derat): Remove this once the normal mode is usable on all platforms.
diff --git a/ash/ash_switches.h b/ash/ash_switches.h
index 251b6af..c26cbe7 100644
--- a/ash/ash_switches.h
+++ b/ash/ash_switches.h
@@ -16,6 +16,7 @@ namespace switches {
 // see chromeos::LoginUtil::GetOffTheRecordCommandLine().)
 
 // Please keep alphabetized.
+ASH_EXPORT extern const char kAshUberTray[];
 ASH_EXPORT extern const char kAuraForceCompactWindowMode[];
 ASH_EXPORT extern const char kAuraGoogleDialogFrames[];
 ASH_EXPORT extern const char kAuraLegacyPowerButton[];
diff --git a/ash/shell.cc b/ash/shell.cc
index c4fcc52..8be3929 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -15,6 +15,10 @@
 #include "ash/shell_delegate.h"
 #include "ash/shell_factory.h"
 #include "ash/shell_window_ids.h"
+#include "ash/system/audio/tray_volume.h"
+#include "ash/system/settings/tray_settings.h"
+#include "ash/system/tray/system_tray_delegate.h"
+#include "ash/system/tray/system_tray.h"
 #include "ash/tooltips/tooltip_controller.h"
 #include "ash/wm/activation_controller.h"
 #include "ash/wm/base_layout_manager.h"
@@ -172,6 +176,46 @@ void CreateSpecialContainers(aura::Window* root_window) {
                   lock_screen_related_containers);
 }
 
+class DummySystemTrayDelegate : public SystemTrayDelegate {
+ public:
+  DummySystemTrayDelegate()
+      : muted_(false),
+        volume_(0.5) {
+  }
+
+  virtual ~DummySystemTrayDelegate() {}
+
+ private:
+
+  // SystemTrayDelegate implementation.
+  virtual void ShowSettings() OVERRIDE {
+  }
+
+  virtual void ShowHelp() OVERRIDE {
+  }
+
+  virtual bool AudioMuted() OVERRIDE {
+    return muted_;
+  }
+
+  virtual void SetAudioMuted(bool muted) OVERRIDE {
+    muted_ = muted;
+  }
+
+  virtual float VolumeLevel() OVERRIDE {
+    return volume_;
+  }
+
+  virtual void SetVolumeLevel(float volume) OVERRIDE {
+    volume_ = volume;
+  }
+
+  bool muted_;
+  float volume_;
+
+  DISALLOW_COPY_AND_ASSIGN(DummySystemTrayDelegate);
+};
+
 }  // namespace
 
 // static
@@ -231,6 +275,9 @@ Shell::~Shell() {
   // deleted as it has a reference to launcher model.
   workspace_controller_.reset();
 
+  // The system tray needs to be reset before all the windows are destroyed.
+  tray_.reset();
+
   // Delete containers now so that child windows does not access
   // observers when they are destructed.
   aura::RootWindow* root_window = GetRootWindow();
@@ -320,6 +367,28 @@ void Shell::Init() {
   if (!status_widget_)
     status_widget_ = internal::CreateStatusArea();
 
+  if (command_line->HasSwitch(switches::kAshUberTray)) {
+    // TODO(sad): This is rather ugly at the moment. This is because we are
+    // supporting both the old and the new status bar at the same time. This
+    // will soon get better once the new one is ready and the old one goes out
+    // the door.
+    if (delegate_.get())
+      status_widget_ = delegate_->CreateStatusArea();
+    if (!status_widget_)
+      status_widget_ = internal::CreateStatusArea();
+    status_widget_->GetContentsView()->RemoveAllChildViews(false);
+    tray_.reset(new SystemTray());
+    status_widget_->GetContentsView()->AddChildView(tray_.get());
+
+    tray_->AddTrayItem(new TrayVolume());
+    tray_->AddTrayItem(new TraySettings());
+
+    if (delegate_.get())
+      tray_delegate_.reset(delegate_->CreateSystemTrayDelegate());
+    if (!tray_delegate_.get())
+      tray_delegate_.reset(new DummySystemTrayDelegate());
+  }
+
   aura::Window* default_container =
       GetContainer(internal::kShellWindowId_DefaultContainer);
   launcher_.reset(new Launcher(default_container));
diff --git a/ash/shell.h b/ash/shell.h
index db60bae..5a57c24 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -42,6 +42,8 @@ class Launcher;
 class NestedDispatcherController;
 class PowerButtonController;
 class ShellDelegate;
+class SystemTrayDelegate;
+class SystemTray;
 class VideoDetector;
 class WindowCycleController;
 
@@ -188,11 +190,14 @@ class ASH_EXPORT Shell {
   }
 
   ShellDelegate* delegate() { return delegate_.get(); }
+  SystemTrayDelegate* tray_delegate() { return tray_delegate_.get(); }
 
   Launcher* launcher() { return launcher_.get(); }
 
   internal::ShelfLayoutManager* shelf() const { return shelf_; }
 
+  SystemTray* tray() const { return tray_.get(); }
+
   // Made available for tests.
   internal::ShadowController* shadow_controller() {
     return shadow_controller_.get();
@@ -240,6 +245,7 @@ class ASH_EXPORT Shell {
 #endif  // !defined(OS_MACOSX)
 
   scoped_ptr<ShellDelegate> delegate_;
+  scoped_ptr<SystemTrayDelegate> tray_delegate_;
 
   scoped_ptr<Launcher> launcher_;
 
@@ -287,6 +293,10 @@ class ASH_EXPORT Shell {
   // Status area with clock, Wi-Fi signal, etc.
   views::Widget* status_widget_;
 
+  // System tray with clock, Wi-Fi signal, etc. (a replacement in progress for
+  // |status_widget_|).
+  scoped_ptr<SystemTray> tray_;
+
   // Offset between the corner of the status area and the corner of the screen
   // when in the compact window mode.
   gfx::Size compact_status_area_offset_;
diff --git a/ash/shell/shell_main.cc b/ash/shell/shell_main.cc
index 7d7715d..86601e9 100644
--- a/ash/shell/shell_main.cc
+++ b/ash/shell/shell_main.cc
@@ -208,6 +208,10 @@ class ShellDelegateImpl : public ash::ShellDelegate {
     return launcher_delegate_;
   }
 
+  virtual ash::SystemTrayDelegate* CreateSystemTrayDelegate() {
+    return NULL;
+  }
+
  private:
   // Used to update Launcher. Owned by main.
   WindowWatcher* watcher_;
diff --git a/ash/shell_delegate.h b/ash/shell_delegate.h
index d4d5f44..55b1a68 100644
--- a/ash/shell_delegate.h
+++ b/ash/shell_delegate.h
@@ -28,6 +28,7 @@ class LauncherDelegate;
 class LauncherModel;
 struct LauncherItem;
 class ScreenshotDelegate;
+class SystemTrayDelegate;
 
 // Delegate of the Shell.
 class ASH_EXPORT ShellDelegate {
@@ -84,6 +85,9 @@ class ASH_EXPORT ShellDelegate {
   // value.
   virtual LauncherDelegate* CreateLauncherDelegate(
       ash::LauncherModel* model) = 0;
+
+  // Creates a system-tray delegate. Shell takes ownership of the delegate.
+  virtual SystemTrayDelegate* CreateSystemTrayDelegate() = 0;
 };
 
 }  // namespace ash
diff --git a/ash/system/audio/tray_volume.cc b/ash/system/audio/tray_volume.cc
new file mode 100644
index 0000000..a8898ac
--- /dev/null
+++ b/ash/system/audio/tray_volume.cc
@@ -0,0 +1,115 @@
+// 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/system/audio/tray_volume.h"
+
+#include "ash/shell.h"
+#include "ash/system/tray/system_tray_delegate.h"
+#include "base/utf_string_conversions.h"
+#include "grit/ui_resources.h"
+#include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/image/image.h"
+#include "ui/views/controls/button/image_button.h"
+#include "ui/views/controls/image_view.h"
+#include "ui/views/controls/label.h"
+#include "ui/views/controls/slider.h"
+#include "ui/views/layout/box_layout.h"
+#include "ui/views/view.h"
+
+namespace tray {
+
+class VolumeView : public views::View,
+                   public views::ButtonListener,
+                   public views::SliderListener {
+ public:
+  VolumeView() {
+    SetLayoutManager(new views::BoxLayout(views::BoxLayout::kHorizontal,
+          0, 0, 5));
+
+    gfx::Image image = ui::ResourceBundle::GetSharedInstance().GetImageNamed(
+        IDR_AURA_UBER_TRAY_VOLUME);
+    icon_ = new views::ToggleImageButton(this);
+    icon_->SetImage(views::CustomButton::BS_NORMAL, image.ToSkBitmap());
+    icon_->SetImage(views::CustomButton::BS_HOT, image.ToSkBitmap());
+    icon_->SetImage(views::CustomButton::BS_PUSHED, image.ToSkBitmap());
+
+    image = ui::ResourceBundle::GetSharedInstance().GetImageNamed(
+        IDR_AURA_UBER_TRAY_VOLUME_MUTE);
+    icon_->SetToggledImage(views::CustomButton::BS_NORMAL, image.ToSkBitmap());
+    icon_->SetToggledImage(views::CustomButton::BS_HOT, image.ToSkBitmap());
+    icon_->SetToggledImage(views::CustomButton::BS_PUSHED, image.ToSkBitmap());
+
+    ash::SystemTrayDelegate* delegate =
+        ash::Shell::GetInstance()->tray_delegate();
+    icon_->SetToggled(delegate->AudioMuted());
+    AddChildView(icon_);
+
+    views::Slider* slider = new views::Slider(this, views::Slider::HORIZONTAL);
+    slider->SetValue(delegate->VolumeLevel());
+    AddChildView(slider);
+    slider->SetVisible(true);
+  }
+
+ private:
+
+  // Overridden from views::ButtonListener.
+  virtual void ButtonPressed(views::Button* sender,
+                             const views::Event& event) OVERRIDE {
+    CHECK(sender == icon_);
+    ash::SystemTrayDelegate* delegate =
+        ash::Shell::GetInstance()->tray_delegate();
+    delegate->SetAudioMuted(!delegate->AudioMuted());
+
+    // TODO(sad): Should the icon auto-update its state when mute/unmute happens
+    // above?
+    icon_->SetToggled(delegate->AudioMuted());
+  }
+
+  // Overridden from views:SliderListener.
+  virtual void SliderValueChanged(views::Slider* sender,
+                                  float value,
+                                  float old_value) OVERRIDE {
+    ash::Shell::GetInstance()->tray_delegate()->SetVolumeLevel(value);
+  }
+
+  views::ToggleImageButton* icon_;
+
+  DISALLOW_COPY_AND_ASSIGN(VolumeView);
+};
+
+}  // namespace tray
+
+TrayVolume::TrayVolume() {
+}
+
+TrayVolume::~TrayVolume() {
+}
+
+views::View* TrayVolume::CreateTrayView() {
+  tray_view_.reset(new views::ImageView());
+  tray_view_->SetImage(ui::ResourceBundle::GetSharedInstance().GetImageNamed(
+        IDR_AURA_UBER_TRAY_VOLUME).ToSkBitmap());
+  return tray_view_.get();
+}
+
+views::View* TrayVolume::CreateDefaultView() {
+  volume_view_.reset(new tray::VolumeView);
+  return volume_view_.get();
+}
+
+views::View* TrayVolume::CreateDetailedView() {
+  NOTIMPLEMENTED();
+  return NULL;
+}
+
+void TrayVolume::DestroyTrayView() {
+  tray_view_.reset();
+}
+
+void TrayVolume::DestroyDefaultView() {
+  volume_view_.reset();
+}
+
+void TrayVolume::DestroyDetailedView() {
+}
diff --git a/ash/system/audio/tray_volume.h b/ash/system/audio/tray_volume.h
new file mode 100644
index 0000000..f43dc33
--- /dev/null
+++ b/ash/system/audio/tray_volume.h
@@ -0,0 +1,40 @@
+// 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.
+
+#ifndef ASH_SYSTEM_AUDIO_TRAY_VOLUME_H_
+#define ASH_SYSTEM_AUDIO_TRAY_VOLUME_H_
+#pragma once
+
+#include "ash/system/tray/system_tray_item.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace views {
+class ImageView;
+}
+
+namespace tray {
+class VolumeView;
+}
+
+class TrayVolume : public ash::SystemTrayItem {
+ public:
+  TrayVolume();
+  virtual ~TrayVolume();
+
+ private:
+  // Overridden from ash::SystemTrayItem
+  virtual views::View* CreateTrayView() OVERRIDE;
+  virtual views::View* CreateDefaultView() OVERRIDE;
+  virtual views::View* CreateDetailedView() OVERRIDE;
+  virtual void DestroyTrayView() OVERRIDE;
+  virtual void DestroyDefaultView() OVERRIDE;
+  virtual void DestroyDetailedView() OVERRIDE;
+
+  scoped_ptr<tray::VolumeView> volume_view_;
+  scoped_ptr<views::ImageView> tray_view_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrayVolume);
+};
+
+#endif  // ASH_SYSTEM_AUDIO_TRAY_VOLUME_H_
diff --git a/ash/system/settings/tray_settings.cc b/ash/system/settings/tray_settings.cc
new file mode 100644
index 0000000..c277c5f
--- /dev/null
+++ b/ash/system/settings/tray_settings.cc
@@ -0,0 +1,95 @@
+// 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/system/settings/tray_settings.h"
+
+#include "ash/shell.h"
+#include "ash/system/tray/system_tray_delegate.h"
+#include "base/logging.h"
+#include "base/utf_string_conversions.h"
+#include "grit/ui_resources.h"
+#include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/image/image.h"
+#include "ui/views/controls/image_view.h"
+#include "ui/views/controls/label.h"
+#include "ui/views/layout/box_layout.h"
+#include "ui/views/layout/fill_layout.h"
+#include "ui/views/view.h"
+
+namespace {
+
+class SettingsView : public views::View {
+ public:
+  SettingsView() {
+    SetLayoutManager(new views::BoxLayout(views::BoxLayout::kHorizontal,
+          0, 0, 3));
+    views::ImageView* icon = new views::ImageView;
+    icon->SetImage(ui::ResourceBundle::GetSharedInstance().
+        GetImageNamed(IDR_AURA_UBER_TRAY_SETTINGS).ToSkBitmap());
+    views::Label* label = new views::Label(ASCIIToUTF16("Settings"));
+
+    AddChildView(icon);
+    AddChildView(label);
+  }
+
+  virtual bool OnMousePressed(const views::MouseEvent& event) OVERRIDE {
+    ash::Shell::GetInstance()->tray_delegate()->ShowSettings();
+    return true;
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SettingsView);
+};
+
+class HelpView : public views::View {
+ public:
+  HelpView() {
+    SetLayoutManager(new views::BoxLayout(views::BoxLayout::kHorizontal,
+          0, 0, 3));
+    views::Label* label = new views::Label(ASCIIToUTF16("Help"));
+    AddChildView(label);
+  }
+
+  virtual bool OnMousePressed(const views::MouseEvent& event) OVERRIDE {
+    ash::Shell::GetInstance()->tray_delegate()->ShowHelp();
+    return true;
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(HelpView);
+};
+
+}  // namespace
+
+views::View* TraySettings::CreateTrayView() {
+  return NULL;
+}
+
+views::View* TraySettings::CreateDefaultView() {
+  views::View* container = new views::View;
+  views::BoxLayout* layout =
+      new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, 5);
+  layout->set_spread_blank_space(true);
+  container->SetLayoutManager(layout);
+
+  views::View* settings = new SettingsView;
+  container->AddChildView(settings);
+  views::View* help = new HelpView;
+  container->AddChildView(help);
+  return container;
+}
+
+views::View* TraySettings::CreateDetailedView() {
+  NOTIMPLEMENTED();
+  return NULL;
+}
+
+void TraySettings::DestroyTrayView() {
+}
+
+void TraySettings::DestroyDefaultView() {
+}
+
+void TraySettings::DestroyDetailedView() {
+}
diff --git a/ash/system/settings/tray_settings.h b/ash/system/settings/tray_settings.h
new file mode 100644
index 0000000..701f1aa
--- /dev/null
+++ b/ash/system/settings/tray_settings.h
@@ -0,0 +1,30 @@
+// 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.
+
+#ifndef ASH_SYSTEM_SETTINGS_TRAY_SETTINGS_H_
+#define ASH_SYSTEM_SETTINGS_TRAY_SETTINGS_H_
+#pragma once
+
+#include "ash/system/tray/system_tray_item.h"
+
+class TraySettings : public ash::SystemTrayItem {
+ public:
+  TraySettings() {
+  }
+
+  virtual ~TraySettings() {}
+
+ private:
+  // Overridden from ash::SystemTrayItem
+  virtual views::View* CreateTrayView() OVERRIDE;
+  virtual views::View* CreateDefaultView() OVERRIDE;
+  virtual views::View* CreateDetailedView() OVERRIDE;
+  virtual void DestroyTrayView() OVERRIDE;
+  virtual void DestroyDefaultView() OVERRIDE;
+  virtual void DestroyDetailedView() OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(TraySettings);
+};
+
+#endif  // ASH_SYSTEM_SETTINGS_TRAY_SETTINGS_H_
diff --git a/ash/system/tray/system_tray.cc b/ash/system/tray/system_tray.cc
new file mode 100644
index 0000000..5b29bbf
--- /dev/null
+++ b/ash/system/tray/system_tray.cc
@@ -0,0 +1,100 @@
+// 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/system/tray/system_tray.h"
+
+#include "ash/shell/panel_window.h"
+#include "ash/system/tray/system_tray_item.h"
+#include "base/logging.h"
+#include "base/utf_string_conversions.h"
+#include "third_party/skia/include/core/SkColor.h"
+#include "ui/views/border.h"
+#include "ui/views/bubble/bubble_delegate.h"
+#include "ui/views/controls/label.h"
+#include "ui/views/layout/box_layout.h"
+#include "ui/views/view.h"
+
+namespace {
+
+const int kTrayIconHeight = 50;
+const int kPadding = 5;
+
+class SystemTrayBubble : public views::BubbleDelegateView {
+ public:
+  explicit SystemTrayBubble(ash::SystemTray* tray)
+      : views::BubbleDelegateView(tray, views::BubbleBorder::BOTTOM_RIGHT),
+        tray_(tray) {
+  }
+
+  virtual ~SystemTrayBubble() {
+    std::vector<ash::SystemTrayItem*> items = tray_->items();
+    for (std::vector<ash::SystemTrayItem*>::iterator it = items.begin();
+        it != items.end();
+        ++it) {
+      (*it)->DestroyDefaultView();
+    }
+  }
+
+ private:
+  // Overridden from views::BubbleDelegateView.
+  virtual void Init() OVERRIDE {
+    SetLayoutManager(new views::BoxLayout(views::BoxLayout::kVertical,
+          0, 0, 1));
+
+    std::vector<ash::SystemTrayItem*> items = tray_->items();
+    for (std::vector<ash::SystemTrayItem*>::iterator it = items.begin();
+        it != items.end();
+        ++it) {
+      views::View* view = (*it)->CreateDefaultView();
+      if (it != items.begin())
+        view->set_border(views::Border::CreateSolidSidedBorder(
+              1, 0, 0, 0, SkColorSetARGB(25, 0, 0, 0)));
+      AddChildView(view);
+    }
+  }
+
+  ash::SystemTray* tray_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemTrayBubble);
+};
+
+}  // namespace
+
+namespace ash {
+
+SystemTray::SystemTray() : items_() {
+  SetLayoutManager(new views::BoxLayout(views::BoxLayout::kHorizontal,
+        5, 10, 3));
+}
+
+SystemTray::~SystemTray() {
+  for (std::vector<ash::SystemTrayItem*>::iterator it = items_.begin();
+      it != items_.end();
+      ++it) {
+    (*it)->DestroyTrayView();
+  }
+}
+
+void SystemTray::AddTrayItem(SystemTrayItem* item) {
+  items_.push_back(item);
+
+  views::View* tray_item = item->CreateTrayView();
+  if (tray_item) {
+    AddChildView(tray_item);
+    PreferredSizeChanged();
+  }
+}
+
+void SystemTray::RemoveTrayItem(SystemTrayItem* item) {
+  NOTIMPLEMENTED();
+}
+
+bool SystemTray::OnMousePressed(const views::MouseEvent& event) {
+  SystemTrayBubble* bubble = new SystemTrayBubble(this);
+  views::BubbleDelegateView::CreateBubble(bubble);
+  bubble->Show();
+  return true;
+}
+
+}  // namespace ash
diff --git a/ash/system/tray/system_tray.h b/ash/system/tray/system_tray.h
new file mode 100644
index 0000000..fb9b8ce
--- /dev/null
+++ b/ash/system/tray/system_tray.h
@@ -0,0 +1,47 @@
+// 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.
+
+#ifndef ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_
+#define ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_
+#pragma once
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "ui/views/view.h"
+
+#include <vector>
+
+namespace views {
+class View;
+}
+
+namespace ash {
+
+class SystemTrayItem;
+
+class ASH_EXPORT SystemTray : public views::View {
+ public:
+  SystemTray();
+  virtual ~SystemTray();
+
+  // Adds a new item in the tray.
+  void AddTrayItem(SystemTrayItem* item);
+
+  // Removes an existing tray item.
+  void RemoveTrayItem(SystemTrayItem* item);
+
+  const std::vector<SystemTrayItem*>& items() const { return items_; }
+
+ private:
+  // Overridden from views::View.
+  virtual bool OnMousePressed(const views::MouseEvent& event) OVERRIDE;
+
+  std::vector<SystemTrayItem*> items_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemTray);
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_
diff --git a/ash/system/tray/system_tray_delegate.h b/ash/system/tray/system_tray_delegate.h
new file mode 100644
index 0000000..7959361
--- /dev/null
+++ b/ash/system/tray/system_tray_delegate.h
@@ -0,0 +1,36 @@
+// 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.
+
+#ifndef ASH_SYSTEM_SYSTEM_DELEGATE_H_
+#define ASH_SYSTEM_SYSTEM_DELEGATE_H_
+#pragma once
+
+namespace ash {
+
+class SystemTrayDelegate {
+ public:
+  virtual ~SystemTrayDelegate(){}
+
+  // Shows settings.
+  virtual void ShowSettings() = 0;
+
+  // Shows help.
+  virtual void ShowHelp() = 0;
+
+  // Is the system muted?
+  virtual bool AudioMuted() = 0;
+
+  // Mutes/Unmutes the system.
+  virtual void SetAudioMuted(bool muted) = 0;
+
+  // Gets volume level.
+  virtual float VolumeLevel() = 0;
+
+  // Sets the volume level.
+  virtual void SetVolumeLevel(float level) = 0;
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_SYSTEM_DELEGATE_H_
diff --git a/ash/system/tray/system_tray_item.cc b/ash/system/tray/system_tray_item.cc
new file mode 100644
index 0000000..ed76fec
--- /dev/null
+++ b/ash/system/tray/system_tray_item.cc
@@ -0,0 +1,21 @@
+// 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/system/tray/system_tray_item.h"
+
+#include "ui/views/view.h"
+
+namespace ash {
+
+SystemTrayItem::SystemTrayItem() {
+}
+
+SystemTrayItem::~SystemTrayItem() {
+}
+
+void SystemTrayItem::PopupDetailedView() {
+  NOTIMPLEMENTED();
+}
+
+}  // namespace ash
diff --git a/ash/system/tray/system_tray_item.h b/ash/system/tray/system_tray_item.h
new file mode 100644
index 0000000..ab0d7e7
--- /dev/null
+++ b/ash/system/tray/system_tray_item.h
@@ -0,0 +1,54 @@
+// 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.
+
+#ifndef ASH_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_
+#define ASH_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_
+#pragma once
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace views {
+class View;
+}
+
+namespace ash {
+
+class ASH_EXPORT SystemTrayItem {
+ public:
+  SystemTrayItem();
+  virtual ~SystemTrayItem();
+
+  // Returns a view to be displayed in the system tray. If this returns NULL,
+  // then this item is not displayed in the tray.
+  virtual views::View* CreateTrayView() = 0;
+
+  // Returns a view for the item to be displayed in the list. This view can be
+  // displayed with a number of other tray items, so this should not be too
+  // big.
+  virtual views::View* CreateDefaultView() = 0;
+
+  // Returns a detailed view for the item. This view is displayed standalone.
+  virtual views::View* CreateDetailedView() = 0;
+
+  // These functions are called when the corresponding view item is about to be
+  // removed. An item should do appropriate cleanup in these functions.
+  virtual void DestroyTrayView() = 0;
+  virtual void DestroyDefaultView() = 0;
+  virtual void DestroyDetailedView() = 0;
+
+  // Pops up the detailed view for this item. An item can request to show its
+  // detailed view using this function (e.g. from an observer callback when
+  // something, e.g. volume, network availability etc. changes).
+  void PopupDetailedView();
+
+ private:
+
+  DISALLOW_COPY_AND_ASSIGN(SystemTrayItem);
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_
diff --git a/ash/test/test_shell_delegate.cc b/ash/test/test_shell_delegate.cc
index 6f7a958..8eb2dfa 100644
--- a/ash/test/test_shell_delegate.cc
+++ b/ash/test/test_shell_delegate.cc
@@ -66,5 +66,8 @@ LauncherDelegate* TestShellDelegate::CreateLauncherDelegate(
   return NULL;
 }
 
+SystemTrayDelegate* TestShellDelegate::CreateSystemTrayDelegate() {
+  return NULL;
+}
 }  // namespace test
 }  // namespace ash
diff --git a/ash/test/test_shell_delegate.h b/ash/test/test_shell_delegate.h
index 6b11557..7400559 100644
--- a/ash/test/test_shell_delegate.h
+++ b/ash/test/test_shell_delegate.h
@@ -32,6 +32,7 @@ class TestShellDelegate : public ShellDelegate {
       ScreenshotDelegate* screenshot_delegate) OVERRIDE;
   virtual LauncherDelegate* CreateLauncherDelegate(
       ash::LauncherModel* model) OVERRIDE;
+  virtual SystemTrayDelegate* CreateSystemTrayDelegate() OVERRIDE;
 };
 
 }  // namespace test