Do not increase volume when user press Volume Up Button to unmute the audio output.

chrome/browser/ui/ash/volume_controller_chromeos.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 "chrome/browser/ui/ash/volume_controller_chromeos.h"
 
 #include "ash/ash_switches.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chromeos/audio/audio_handler.h"
 #include "chrome/browser/extensions/api/system_private/system_private_api.h"
@@ skipping 68 matching lines @@
 
 bool VolumeController::HandleVolumeUp(const ui::Accelerator& accelerator) {
   if (accelerator.key_code() == ui::VKEY_VOLUME_UP)
     content::RecordAction(content::UserMetricsAction("Accel_VolumeUp_F10"));
 
   if (ash::switches::UseNewAudioHandler()) {
     CrasAudioHandler* audio_handler = CrasAudioHandler::Get();
 
     if (audio_handler->IsOutputMuted())
       audio_handler->SetOutputMute(false);
-    audio_handler->AdjustOutputVolumeByPercent(kStepPercentage);
+    else
+      audio_handler->AdjustOutputVolumeByPercent(kStepPercentage);
     return true;
   }
 
   chromeos::AudioHandler* audio_handler = chromeos::AudioHandler::GetInstance();
   if (audio_handler->IsMuted()) {
     audio_handler->SetMuted(false);
   } else {
     audio_handler->AdjustVolumeByPercent(kStepPercentage);
   }
 
@@ skipping 39 matching lines @@
       audio_handler->IsOutputMuted());
 }
 
 void VolumeController::OnOutputMuteChanged() {
   DCHECK(ash::switches::UseNewAudioHandler());
   CrasAudioHandler* audio_handler = CrasAudioHandler::Get();
   extensions::DispatchVolumeChangedEvent(
       audio_handler->GetOutputVolumePercent(),
       audio_handler->IsOutputMuted());
 }