Modify the volume visuals:

ash/system/audio/tray_volume.cc

Index: ash/system/audio/tray_volume.cc
diff --git a/ash/system/audio/tray_volume.cc b/ash/system/audio/tray_volume.cc
index fba2fe871c0c8307da27b1e97d94558d5f3ab7f9..07cb048e1f4565b56b4a0dfbeed5bb0ff9bf98f1 100644
--- a/ash/system/audio/tray_volume.cc
+++ b/ash/system/audio/tray_volume.cc
@@ -106,7 +106,8 @@ class VolumeView : public views::View,
         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));
@@ -148,8 +149,11 @@ class VolumeView : public views::View,
                                   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();
   }
 
@@ -171,7 +175,9 @@ 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) {
@@ -201,6 +207,8 @@ void TrayVolume::OnVolumeChanged(float percent) {
     tray_view()->SetVisible(GetInitialVisibility());
 
   if (volume_view_) {
+    if (ash::Shell::GetInstance()->tray_delegate()->IsAudioMuted())
+      percent = 0.0;
     volume_view_->SetVolumeLevel(percent);
     SetDetailedViewCloseDelay(kTrayPopupAutoCloseDelayInSeconds);
     return;