Modify the volume visuals:

ash/system/audio/tray_volume.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/system/audio/tray_volume.h"
 
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_views.h"
@@ skipping 88 matching lines @@
     SetLayoutManager(new views::BoxLayout(views::BoxLayout::kHorizontal,
           kTrayPopupPaddingHorizontal, 0, kTrayPopupPaddingBetweenItems));
 
     icon_ = new VolumeButton(this);
     AddChildView(icon_);
 
     ash::SystemTrayDelegate* delegate =
         ash::Shell::GetInstance()->tray_delegate();
     slider_ = new views::Slider(this, views::Slider::HORIZONTAL);
     slider_->set_focus_border_color(kFocusBorderColor);
-    slider_->SetValue(delegate->GetVolumeLevel());
+    slider_->SetValue(
+        delegate->IsAudioMuted() ? 0.0 :  delegate->GetVolumeLevel());

[Daniel Erat, 2012/05/21 17:45:43]

nit: remove extra space after ":" (you have two)

[Jun Mukai, 2012/05/21 17:56:07]

Done.

     slider_->SetAccessibleName(
         ui::ResourceBundle::GetSharedInstance().GetLocalizedString(
             IDS_ASH_STATUS_TRAY_VOLUME));
     AddChildView(slider_);
   }
 
   virtual ~VolumeView() {}
 
   void SetVolumeLevel(float percent) {
     // The change in volume will be reflected via accessibility system events,
@@ skipping 21 matching lines @@
     ash::SystemTrayDelegate* delegate =
         ash::Shell::GetInstance()->tray_delegate();
     delegate->SetAudioMuted(!delegate->IsAudioMuted());
   }
 
   // Overridden from views:SliderListener.
   virtual void SliderValueChanged(views::Slider* sender,
                                   float value,
                                   float old_value,
                                   views::SliderChangeReason reason) OVERRIDE {
-    if (reason == views::VALUE_CHANGED_BY_USER)
-      ash::Shell::GetInstance()->tray_delegate()->SetVolumeLevel(value);
+    if (reason == views::VALUE_CHANGED_BY_USER) {
+      ash::SystemTrayDelegate* delegate =
+          ash::Shell::GetInstance()->tray_delegate();
+      delegate->SetVolumeLevel(value);
+    }
     icon_->Update();
   }
 
   VolumeButton* icon_;
   views::Slider* slider_;
 
   DISALLOW_COPY_AND_ASSIGN(VolumeView);
 };
 
 }  // namespace tray
 
 TrayVolume::TrayVolume()
     : TrayImageItem(IDR_AURA_UBER_TRAY_VOLUME_MUTE),
       volume_view_(NULL),
       is_default_view_(false) {
 }
 
 TrayVolume::~TrayVolume() {
 }
 
 bool TrayVolume::GetInitialVisibility() {
-  return ash::Shell::GetInstance()->tray_delegate()->IsAudioMuted();
+  ash::SystemTrayDelegate* delegate =
+      ash::Shell::GetInstance()->tray_delegate();
+  return delegate->GetVolumeLevel() == 0.0 || delegate->IsAudioMuted();
 }
 
 views::View* TrayVolume::CreateDefaultView(user::LoginStatus status) {
   volume_view_ = new tray::VolumeView;
   is_default_view_ = true;
   return volume_view_;
 }
 
 views::View* TrayVolume::CreateDetailedView(user::LoginStatus status) {
   volume_view_ = new tray::VolumeView;
   is_default_view_ = false;
   return volume_view_;
 }
 
 void TrayVolume::DestroyDefaultView() {
   if (is_default_view_)
     volume_view_ = NULL;
 }
 
 void TrayVolume::DestroyDetailedView() {
   if (!is_default_view_)
     volume_view_ = NULL;
 }
 
 void TrayVolume::OnVolumeChanged(float percent) {
   if (tray_view())
     tray_view()->SetVisible(GetInitialVisibility());
 
   if (volume_view_) {
+    if (ash::Shell::GetInstance()->tray_delegate()->IsAudioMuted())
+      percent = 0.0;
     volume_view_->SetVolumeLevel(percent);
     SetDetailedViewCloseDelay(kTrayPopupAutoCloseDelayInSeconds);
     return;
   }
   PopupDetailedView(kTrayPopupAutoCloseDelayInSeconds, false);
 }
 
 }  // namespace internal
 }  // namespace ash