Improve Bluetooth tethering UI usability.

- Updated hint text for BT tethering checkbox to
  "[Sharing|not sharing] this [tablet|phone]'s mobile data connection".
- Show correct hint text when user enters tethering screen.
- Show correct status after user enables tethering when Bluetooth is off.
  When BluetoothPan.setBluetoothTethering(true) is called with BT off,
  BluetoothPanProfileHandler will add a broadcast receiver to enable
  tethering after BT turns on. This happens too late to show the correct
  status when TetherSettings gets the adapter state changed event, so set
  a flag (mBluetoothEnableForTether) instead, and call setBluetoothTethering
  ourselves after the state changes to ON. Also, clear the flag if the
  adapter state changes to OFF or ERROR.
- Show correct status when user enables tethering, then disables Bluetooth,
  then returns to the tethering screen. Previously it would show
  Bluetooth tethering enabled, even though adapter state was OFF.
- Show the number of connected devices in tethering preference screen.
- Distinguish between PANU and NAP in device profiles screen, and show
  appropriate text to clarify the direction of tethering.
- Remove profiles from device profiles list when the device removes the UUID
  (e.g. Mac OS X turning NAP on/off) and after a NAP disconnection when the
  remote device only supports PANU.

Bug: 3414575
Change-Id: I2c0830876d5b9bddb293e57c4d3ca74f105911b8

src/com/android/settings/bluetooth/HeadsetProfile.java

@@ -22,13 +22,11 @@ import android.bluetooth.BluetoothHeadset;
 import android.bluetooth.BluetoothProfile;
 import android.bluetooth.BluetoothUuid;
 import android.content.Context;
-import android.os.Handler;
 import android.os.ParcelUuid;
 import android.util.Log;
 
 import com.android.settings.R;
 
-import java.util.ArrayList;
 import java.util.List;
 
 /**
@@ -176,7 +174,7 @@ final class HeadsetProfile implements LocalBluetoothProfile {
         return R.string.bluetooth_profile_headset;
     }
 
-    public int getDisconnectResource() {
+    public int getDisconnectResource(BluetoothDevice device) {
         return R.string.bluetooth_disconnect_headset_profile;
     }