Reland "Refactor audio manager for Android to avoid heavy tasks at startup"

media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java

Index: media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
diff --git a/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java b/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
index afaa0358ec184f956b2616f0037b33f699454f1e..15d7aef6959d78bcd0bd527a16ecbfe7f3051694 100644
--- a/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
+++ b/media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
@@ -4,8 +4,6 @@
 
 package org.chromium.media;
 
-import android.bluetooth.BluetoothAdapter;
-import android.bluetooth.BluetoothManager;
 import android.content.BroadcastReceiver;
 import android.content.ContentResolver;
 import android.content.Context;
@@ -20,8 +18,7 @@ import android.media.AudioTrack;
 import android.media.audiofx.AcousticEchoCanceler;
 import android.os.Build;
 import android.os.Handler;
-import android.os.Looper;
-import android.os.Process;
+import android.os.HandlerThread;
 import android.provider.Settings;
 import android.util.Log;
 
@@ -57,6 +54,7 @@ class AudioManagerAndroid {
     }
 
     // Supported audio device types.
+    private static final int DEVICE_DEFAULT = -2;
     private static final int DEVICE_INVALID = -1;
     private static final int DEVICE_SPEAKERPHONE = 0;
     private static final int DEVICE_WIRED_HEADSET = 1;
@@ -83,24 +81,6 @@ class AudioManagerAndroid {
         DEVICE_BLUETOOTH_HEADSET,
     };
 
-    // The device does not have any audio device.
-    static final int STATE_NO_DEVICE_SELECTED = 0;
-    // The speakerphone is on and an associated microphone is used.
-    static final int STATE_SPEAKERPHONE_ON = 1;
-    // The phone's earpiece is on and an associated microphone is used.
-    static final int STATE_EARPIECE_ON = 2;
-    // A wired headset (with or without a microphone) is plugged in.
-    static final int STATE_WIRED_HEADSET_ON = 3;
-    // The audio stream is being directed to a Bluetooth headset.
-    static final int STATE_BLUETOOTH_ON = 4;
-    // We've requested that the audio stream be directed to Bluetooth, but
-    // have not yet received a response from the framework.
-    static final int STATE_BLUETOOTH_TURNING_ON = 5;
-    // We've requested that the audio stream stop being directed to
-    // Bluetooth, but have not yet received a response from the framework.
-    static final int STATE_BLUETOOTH_TURNING_OFF = 6;
-    // TODO(henrika): document the valid state transitions.
-
     // Use 44.1kHz as the default sampling rate.
     private static final int DEFAULT_SAMPLING_RATE = 44100;
     // Randomly picked up frame size which is close to return value on N4.
@@ -112,15 +92,18 @@ class AudioManagerAndroid {
     private final Context mContext;
     private final long mNativeAudioManagerAndroid;
 
-    private boolean mHasBluetoothPermission = false;
+    private int mSavedAudioMode = AudioManager.MODE_INVALID;
+
     private boolean mIsInitialized = false;
     private boolean mSavedIsSpeakerphoneOn;
     private boolean mSavedIsMicrophoneMute;
 
-    private Integer mAudioDeviceState = STATE_NO_DEVICE_SELECTED;
+    // Id of the requested audio device. Can only be modified by
+    // call to setDevice().
+    private int mRequestedAudioDevice = DEVICE_INVALID;
 
-    // Lock to protect |mAudioDevices| which can be accessed from the main
-    // thread and the audio manager thread.
+    // Lock to protect |mAudioDevices| and |mRequestedAudioDevice| which can
+    // be accessed from the main thread and the audio manager thread.
     private final Object mLock = new Object();
 
     // Contains a list of currently available audio devices.
@@ -128,9 +111,8 @@ class AudioManagerAndroid {
 
     private final ContentResolver mContentResolver;
     private SettingsObserver mSettingsObserver = null;
-    private SettingsObserverThread mSettingsObserverThread = null;
+    private HandlerThread mSettingsObserverThread = null;
     private int mCurrentVolume;
-    private final Object mSettingsObserverLock = new Object();
 
     // Broadcast receiver for wired headset intent broadcasts.
     private BroadcastReceiver mWiredHeadsetReceiver;
@@ -157,56 +139,31 @@ class AudioManagerAndroid {
      */
     @CalledByNative
     public void init() {
+        if (DEBUG) logd("init");
         if (mIsInitialized)
             return;
 
-        synchronized (mLock) {
-            for (int i = 0; i < DEVICE_COUNT; ++i) {
-                mAudioDevices[i] = false;
-            }
+        for (int i = 0; i < DEVICE_COUNT; ++i) {
+            mAudioDevices[i] = false;
         }
 
-        // Store microphone mute state and speakerphone state so it can
-        // be restored when closing.
-        mSavedIsSpeakerphoneOn = mAudioManager.isSpeakerphoneOn();
-        mSavedIsMicrophoneMute = mAudioManager.isMicrophoneMute();
-
-        // Always enable speaker phone by default. This state might be reset
-        // by the wired headset receiver when it gets its initial sticky
-        // intent, if any.
-        setSpeakerphoneOn(true);
-        mAudioDeviceState = STATE_SPEAKERPHONE_ON;
-
         // Initialize audio device list with things we know is always available.
-        synchronized (mLock) {
-            if (hasEarpiece()) {
-                mAudioDevices[DEVICE_EARPIECE] = true;
-            }
-            mAudioDevices[DEVICE_SPEAKERPHONE] = true;
+        if (hasEarpiece()) {
+            mAudioDevices[DEVICE_EARPIECE] = true;
         }
+        mAudioDevices[DEVICE_SPEAKERPHONE] = true;
 
         // Register receiver for broadcasted intents related to adding/
         // removing a wired headset (Intent.ACTION_HEADSET_PLUG).
-        // Also starts routing to the wired headset/headphone if one is
-        // already attached (can be overridden by a Bluetooth headset).
         registerForWiredHeadsetIntentBroadcast();
 
-        // Start routing to Bluetooth if there's a connected device.
-        // TODO(henrika): the actual routing part is not implemented yet.
-        // All we do currently is to detect if BT headset is attached or not.
-        initBluetooth();
+        mSettingsObserverThread = new HandlerThread("SettingsObserver");
+        mSettingsObserverThread.start();
+        mSettingsObserver = new SettingsObserver(
+            new Handler(mSettingsObserverThread.getLooper()));
 
         mIsInitialized = true;
-
-        mSettingsObserverThread = new SettingsObserverThread();
-        mSettingsObserverThread.start();
-        synchronized (mSettingsObserverLock) {
-            try {
-                mSettingsObserverLock.wait();
-            } catch (InterruptedException e) {
-                Log.e(TAG, "unregisterHeadsetReceiver exception: " + e.getMessage());
-            }
-        }
+        if (DEBUG) reportUpdate();
     }
 
     /**
@@ -215,33 +172,79 @@ class AudioManagerAndroid {
      */
     @CalledByNative
     public void close() {
+        if (DEBUG) logd("close");
         if (!mIsInitialized)
             return;
 
-        if (mSettingsObserverThread != null) {
-            mSettingsObserverThread = null;
-        }
-        if (mSettingsObserver != null) {
-            mContentResolver.unregisterContentObserver(mSettingsObserver);
-            mSettingsObserver = null;
+        mSettingsObserverThread.quit();
+        try {
+            mSettingsObserverThread.join();
+        } catch (InterruptedException e) {
+            logwtf("HandlerThread.join() exception: " + e.getMessage());
         }
+        mSettingsObserverThread = null;
+        mContentResolver.unregisterContentObserver(mSettingsObserver);
+        mSettingsObserver = null;
 
         unregisterForWiredHeadsetIntentBroadcast();
 
-        // Restore previously stored audio states.
-        setMicrophoneMute(mSavedIsMicrophoneMute);
-        setSpeakerphoneOn(mSavedIsSpeakerphoneOn);
-
         mIsInitialized = false;
     }
 
+    /**
+     * Saves current audio mode and sets audio mode to MODE_IN_COMMUNICATION
+     * if input parameter is true. Restores saved audio mode if input parameter
+     * is false.
+     */
     @CalledByNative
-    public void setMode(int mode) {
-        try {
-            mAudioManager.setMode(mode);
-        } catch (SecurityException e) {
-            Log.e(TAG, "setMode exception: " + e.getMessage());
-            logDeviceInfo();
+    private void setCommunicationAudioModeOn(boolean on) {
+        if (DEBUG) logd("setCommunicationAudioModeOn(" + on + ")");
+
+        if (on) {
+            if (mSavedAudioMode != AudioManager.MODE_INVALID) {
+                logwtf("Audio mode has already been set!");
+                return;
+            }
+
+            // Store the current audio mode the first time we try to
+            // switch to communication mode.
+            try {
+                mSavedAudioMode = mAudioManager.getMode();
+            } catch (SecurityException e) {
+                logwtf("getMode exception: " + e.getMessage());
+                logDeviceInfo();
+            }
+
+            // Store microphone mute state and speakerphone state so it can
+            // be restored when closing.
+            mSavedIsSpeakerphoneOn = mAudioManager.isSpeakerphoneOn();
+            mSavedIsMicrophoneMute = mAudioManager.isMicrophoneMute();
+
+            try {
+                mAudioManager.setMode(AudioManager.MODE_IN_COMMUNICATION);
+            } catch (SecurityException e) {
+                logwtf("setMode exception: " + e.getMessage());
+                logDeviceInfo();
+            }
+        } else {
+            if (mSavedAudioMode == AudioManager.MODE_INVALID) {
+                logwtf("Audio mode has not yet been set!");
+                return;
+            }
+
+            // Restore previously stored audio states.
+            setMicrophoneMute(mSavedIsMicrophoneMute);
+            setSpeakerphoneOn(mSavedIsSpeakerphoneOn);
+
+            // Restore the mode that was used before we switched to
+            // communication mode.
+            try {
+                mAudioManager.setMode(mSavedAudioMode);
+            } catch (SecurityException e) {
+                logwtf("setMode exception: " + e.getMessage());
+                logDeviceInfo();
+            }
+            mSavedAudioMode = AudioManager.MODE_INVALID;
         }
     }
 
@@ -250,40 +253,36 @@ class AudioManagerAndroid {
      *
      * @param deviceId Unique device ID (integer converted to string)
      * representing the selected device. This string is empty if the so-called
-     * default device is selected.
+     * default device is requested.
      */
     @CalledByNative
-    public void setDevice(String deviceId) {
-        boolean devices[] = null;
-        synchronized (mLock) {
-            devices = mAudioDevices.clone();
-        }
-        if (deviceId.isEmpty()) {
-            logd("setDevice: default");
-            // Use a special selection scheme if the default device is selected.
-            // The "most unique" device will be selected; Bluetooth first, then
-            // wired headset and last the speaker phone.
-            if (devices[DEVICE_BLUETOOTH_HEADSET]) {
-                // TODO(henrika): possibly need improvements here if we are
-                // in a STATE_BLUETOOTH_TURNING_OFF state.
-                setAudioDevice(DEVICE_BLUETOOTH_HEADSET);
-            } else if (devices[DEVICE_WIRED_HEADSET]) {
-                setAudioDevice(DEVICE_WIRED_HEADSET);
-            } else {
-                setAudioDevice(DEVICE_SPEAKERPHONE);
-            }
-        } else {
-            logd("setDevice: " + deviceId);
-            // A non-default device is specified. Verify that it is valid
-            // device, and if so, start using it.
-            List<Integer> validIds = Arrays.asList(VALID_DEVICES);
-            Integer id = Integer.valueOf(deviceId);
-            if (validIds.contains(id)) {
-                setAudioDevice(id.intValue());
-            } else {
-                loge("Invalid device ID!");
+    private boolean setDevice(String deviceId) {
+        if (DEBUG) logd("setDevice: " + deviceId);
+        int intDeviceId = deviceId.isEmpty() ?
+            DEVICE_DEFAULT : Integer.parseInt(deviceId);
+
+        if (intDeviceId == DEVICE_DEFAULT) {
+            boolean devices[] = null;
+            synchronized (mLock) {
+                devices = mAudioDevices.clone();
+                mRequestedAudioDevice = DEVICE_DEFAULT;
             }
+            int defaultDevice = selectDefaultDevice(devices);
+            setAudioDevice(defaultDevice);
+            return true;
         }
+
+        // A non-default device is specified. Verify that it is valid
+        // device, and if so, start using it.
+        List<Integer> validIds = Arrays.asList(VALID_DEVICES);
+        if (!validIds.contains(intDeviceId) || !mAudioDevices[intDeviceId]) {
+            return false;
+        }
+        synchronized (mLock) {
+            mRequestedAudioDevice = intDeviceId;
+        }
+        setAudioDevice(intDeviceId);
+        return true;
     }
 
     /**
@@ -293,20 +292,23 @@ class AudioManagerAndroid {
      */
     @CalledByNative
     public AudioDeviceName[] getAudioInputDeviceNames() {
+        boolean devices[] = null;
         synchronized (mLock) {
-            List<String> devices = new ArrayList<String>();
-            AudioDeviceName[] array = new AudioDeviceName[getNumOfAudioDevicesWithLock()];
-            int i = 0;
-            for (int id = 0; id < DEVICE_COUNT; ++id) {
-                if (mAudioDevices[id]) {
-                    array[i] = new AudioDeviceName(id, DEVICE_NAMES[id]);
-                    devices.add(DEVICE_NAMES[id]);
-                    i++;
-                }
+            devices = mAudioDevices.clone();
+        }
+        List<String> list = new ArrayList<String>();
+        AudioDeviceName[] array =
+            new AudioDeviceName[getNumOfAudioDevices(devices)];
+        int i = 0;
+        for (int id = 0; id < DEVICE_COUNT; ++id) {
+            if (devices[id]) {
+                array[i] = new AudioDeviceName(id, DEVICE_NAMES[id]);
+                list.add(DEVICE_NAMES[id]);
+                i++;
             }
-            logd("getAudioInputDeviceNames: " + devices);
-            return array;
         }
+        if (DEBUG) logd("getAudioInputDeviceNames: " + list);
+        return array;
     }
 
     @CalledByNative
@@ -387,7 +389,7 @@ class AudioManagerAndroid {
     }
 
     /** Sets the speaker phone mode. */
-    public void setSpeakerphoneOn(boolean on) {
+    private void setSpeakerphoneOn(boolean on) {
         boolean wasOn = mAudioManager.isSpeakerphoneOn();
         if (wasOn == on) {
             return;
@@ -396,7 +398,7 @@ class AudioManagerAndroid {
     }
 
     /** Sets the microphone mute state. */
-    public void setMicrophoneMute(boolean on) {
+    private void setMicrophoneMute(boolean on) {
         boolean wasMuted = mAudioManager.isMicrophoneMute();
         if (wasMuted == on) {
             return;
@@ -405,7 +407,7 @@ class AudioManagerAndroid {
     }
 
     /** Gets  the current microphone mute state. */
-    public boolean isMicrophoneMute() {
+    private boolean isMicrophoneMute() {
         return mAudioManager.isMicrophoneMute();
     }
 
@@ -424,7 +426,9 @@ class AudioManagerAndroid {
         IntentFilter filter = new IntentFilter(Intent.ACTION_HEADSET_PLUG);
 
         /**
-         * Receiver which handles changes in wired headset availablilty.
+         * Receiver which handles changes in wired headset availability:
+         *   updates the list of devices;
+         *   updates the active device if a device selection has been made.
          */
         mWiredHeadsetReceiver = new BroadcastReceiver() {
             private static final int STATE_UNPLUGGED = 0;
@@ -439,13 +443,14 @@ class AudioManagerAndroid {
                     return;
                 }
                 int state = intent.getIntExtra("state", STATE_UNPLUGGED);
-                int microphone = intent.getIntExtra("microphone", HAS_NO_MIC);
-                String name = intent.getStringExtra("name");
-                logd("==> onReceive: s=" + state
+                if (DEBUG) {
+                    int microphone = intent.getIntExtra("microphone", HAS_NO_MIC);
+                    String name = intent.getStringExtra("name");
+                    logd("BroadcastReceiver.onReceive: s=" + state
                         + ", m=" + microphone
                         + ", n=" + name
                         + ", sb=" + isInitialStickyBroadcast());
-
+                }
                 switch (state) {
                     case STATE_UNPLUGGED:
                         synchronized (mLock) {
@@ -455,27 +460,30 @@ class AudioManagerAndroid {
                                 mAudioDevices[DEVICE_EARPIECE] = true;
                             }
                         }
-                        // If wired headset was used before it was unplugged,
-                        // switch to speaker phone. If it was not in use; just
-                        // log the change.
-                        if (mAudioDeviceState == STATE_WIRED_HEADSET_ON) {
-                            setAudioDevice(DEVICE_SPEAKERPHONE);
-                        } else {
-                            reportUpdate();
-                        }
                         break;
                     case STATE_PLUGGED:
                         synchronized (mLock) {
                             // Wired headset and earpiece are mutually exclusive.
                             mAudioDevices[DEVICE_WIRED_HEADSET] = true;
                             mAudioDevices[DEVICE_EARPIECE] = false;
-                            setAudioDevice(DEVICE_WIRED_HEADSET);
                         }
                         break;
                     default:
                         loge("Invalid state!");
                         break;
                 }
+
+                // Update the existing device selection, but only if a specific
+                // device has already been selected explicitly.
+                boolean deviceHasBeenRequested = false;
+                synchronized (mLock) {
+                    deviceHasBeenRequested = (mRequestedAudioDevice != DEVICE_INVALID);
+                }
+                if (deviceHasBeenRequested) {
+                    updateDeviceActivation();
+                } else if (DEBUG) {
+                    reportUpdate();
+                }
             }
         };
 
@@ -492,62 +500,11 @@ class AudioManagerAndroid {
     }
 
     /**
-    * Check if Bluetooth device is connected, register Bluetooth receiver
-    * and start routing to Bluetooth if a device is connected.
-    * TODO(henrika): currently only supports the detecion part at startup.
-    */
-    private void initBluetooth() {
-        // Bail out if we don't have the required permission.
-        mHasBluetoothPermission = mContext.checkPermission(
-            android.Manifest.permission.BLUETOOTH,
-            Process.myPid(),
-            Process.myUid()) == PackageManager.PERMISSION_GRANTED;
-        if (!mHasBluetoothPermission) {
-            loge("BLUETOOTH permission is missing!");
-            return;
-        }
-
-        // To get a BluetoothAdapter representing the local Bluetooth adapter,
-        // when running on JELLY_BEAN_MR1 (4.2) and below, call the static
-        // getDefaultAdapter() method; when running on JELLY_BEAN_MR2 (4.3) and
-        // higher, retrieve it through getSystemService(String) with
-        // BLUETOOTH_SERVICE.
-        // Note: Most methods require the BLUETOOTH permission.
-        BluetoothAdapter btAdapter = null;
-        if (android.os.Build.VERSION.SDK_INT <=
-            android.os.Build.VERSION_CODES.JELLY_BEAN_MR1) {
-            // Use static method for Android 4.2 and below to get the
-            // BluetoothAdapter.
-            btAdapter = BluetoothAdapter.getDefaultAdapter();
-        } else {
-            // Use BluetoothManager to get the BluetoothAdapter for
-            // Android 4.3 and above.
-            BluetoothManager btManager = (BluetoothManager) mContext.getSystemService(
-                    Context.BLUETOOTH_SERVICE);
-            btAdapter = btManager.getAdapter();
-        }
-
-        if (btAdapter != null &&
-            // android.bluetooth.BluetoothAdapter.getProfileConnectionState
-            // requires BLUETOOTH permission.
-            android.bluetooth.BluetoothProfile.STATE_CONNECTED ==
-                    btAdapter.getProfileConnectionState(
-                            android.bluetooth.BluetoothProfile.HEADSET)) {
-            synchronized (mLock) {
-                mAudioDevices[DEVICE_BLUETOOTH_HEADSET] = true;
-            }
-            // TODO(henrika): ensure that we set the active audio
-            // device to Bluetooth (not trivial).
-            setAudioDevice(DEVICE_BLUETOOTH_HEADSET);
-        }
-    }
-
-    /**
      * Changes selection of the currently active audio device.
      *
      * @param device Specifies the selected audio device.
      */
-    public void setAudioDevice(int device) {
+    private void setAudioDevice(int device) {
         switch (device) {
             case DEVICE_BLUETOOTH_HEADSET:
                 // TODO(henrika): add support for turning on an routing to
@@ -556,17 +513,14 @@ class AudioManagerAndroid {
                 break;
             case DEVICE_SPEAKERPHONE:
                 // TODO(henrika): turn off BT if required.
-                mAudioDeviceState = STATE_SPEAKERPHONE_ON;
                 setSpeakerphoneOn(true);
                 break;
             case DEVICE_WIRED_HEADSET:
                 // TODO(henrika): turn off BT if required.
-                mAudioDeviceState = STATE_WIRED_HEADSET_ON;
                 setSpeakerphoneOn(false);
                 break;
             case DEVICE_EARPIECE:
                 // TODO(henrika): turn off BT if required.
-                mAudioDeviceState = STATE_EARPIECE_ON;
                 setSpeakerphoneOn(false);
                 break;
             default:
@@ -576,11 +530,58 @@ class AudioManagerAndroid {
         reportUpdate();
     }
 
-    private int getNumOfAudioDevicesWithLock() {
+    /**
+     * Use a special selection scheme if the default device is selected.
+     * The "most unique" device will be selected; Wired headset first,
+     * then Bluetooth and last the speaker phone.
+     */
+    private static int selectDefaultDevice(boolean[] devices) {
+        if (devices[DEVICE_WIRED_HEADSET]) {
+            return DEVICE_WIRED_HEADSET;
+        } else if (devices[DEVICE_BLUETOOTH_HEADSET]) {
+            // TODO(henrika): possibly need improvements here if we are
+            // in a state where Bluetooth is turning off.
+            return DEVICE_BLUETOOTH_HEADSET;
+        }
+        return DEVICE_SPEAKERPHONE;
+    }
+
+    /**
+     * Updates the active device given the current list of devices and
+     * information about if a specific device has been selected or if
+     * the default device is selected.
+     */
+    private void updateDeviceActivation() {
+        boolean devices[] = null;
+        int requested = DEVICE_INVALID;
+        synchronized (mLock) {
+            requested = mRequestedAudioDevice;
+            devices = mAudioDevices.clone();
+        }
+        if (requested == DEVICE_INVALID) {
+            loge("Unable to activate device since no device is selected!");
+            return;
+        }
+
+        // Update default device if it has been selected explicitly, or
+        // the selected device has been removed from the list.
+        if (requested == DEVICE_DEFAULT || !devices[requested]) {
+            // Get default device given current list and activate the device.
+            int defaultDevice = selectDefaultDevice(devices);
+            setAudioDevice(defaultDevice);
+        } else {
+            // Activate the selected device since we know that it exists in
+            // the list.
+            setAudioDevice(requested);
+        }
+    }
+
+    /** Returns number of available devices */
+    private static int getNumOfAudioDevices(boolean[] devices) {
         int count = 0;
         for (int i = 0; i < DEVICE_COUNT; ++i) {
-            if (mAudioDevices[i])
-                count++;
+            if (devices[i])
+                ++count;
         }
         return count;
     }
@@ -598,8 +599,10 @@ class AudioManagerAndroid {
                 if (mAudioDevices[i])
                     devices.add(DEVICE_NAMES[i]);
             }
-            logd("reportUpdate: state=" + mAudioDeviceState
-                + ", devices=" + devices);
+            if (DEBUG) {
+                logd("reportUpdate: requested=" + mRequestedAudioDevice
+                    + ", devices=" + devices);
+            }
         }
     }
 
@@ -619,39 +622,26 @@ class AudioManagerAndroid {
         Log.e(TAG, msg);
     }
 
+    /** What a Terrible Failure: Reports a condition that should never happen */
+    private void logwtf(String msg) {
+        Log.wtf(TAG, msg);
+    }
+
     private class SettingsObserver extends ContentObserver {
-        SettingsObserver() {
-            super(new Handler());
+        SettingsObserver(Handler handler) {
+            super(handler);
             mContentResolver.registerContentObserver(Settings.System.CONTENT_URI, true, this);
         }
 
         @Override
         public void onChange(boolean selfChange) {
+            if (DEBUG) logd("SettingsObserver.onChange: " + selfChange);
             super.onChange(selfChange);
             int volume = mAudioManager.getStreamVolume(AudioManager.STREAM_VOICE_CALL);
+            if (DEBUG) logd("nativeSetMute: " + (volume == 0));
             nativeSetMute(mNativeAudioManagerAndroid, (volume == 0));
         }
     }
 
     private native void nativeSetMute(long nativeAudioManagerAndroid, boolean muted);
-
-    private class SettingsObserverThread extends Thread {
-        SettingsObserverThread() {
-            super("SettinsObserver");
-        }
-
-        @Override
-        public void run() {
-            // Set this thread up so the handler will work on it.
-            Looper.prepare();
-
-            synchronized (mSettingsObserverLock) {
-                mSettingsObserver = new SettingsObserver();
-                mSettingsObserverLock.notify();
-            }
-
-            // Listen for volume change.
-            Looper.loop();
-        }
-    }
 }