Update Settings UI regarding tethering.

If tethering is disabled (build var or a gservices property) for the device,
don't show any of the tethering options.  If Usb Tethering is disabled (config.xml) don't show
Usb Options.  If Wifi Tethering is disabled (config.xml) don't show Wifi Options.
diff --git a/src/com/android/settings/TetherSettings.java b/src/com/android/settings/TetherSettings.java
index 0a63de3..1e9c4e2 100644
--- a/src/com/android/settings/TetherSettings.java
+++ b/src/com/android/settings/TetherSettings.java
@@ -30,6 +30,7 @@
 import android.provider.Settings;
 import android.util.Log;
 
+import java.util.ArrayList;
 /*
  * Displays preferences for Tethering.
  */
@@ -43,6 +44,12 @@
 
     private BroadcastReceiver mTetherChangeReceiver;
 
+    private String[] mUsbRegexs;
+    private ArrayList mUsbIfaces;
+
+    private String[] mWifiRegexs;
+    private ArrayList mWifiIfaces;
+
     @Override
     protected void onCreate(Bundle icicle) {
         super.onCreate(icicle);
@@ -51,12 +58,27 @@
 
         mEnableTetherNotice = (CheckBoxPreference) findPreference(ENABLE_TETHER_NOTICE);
         mUsbTether = (PreferenceScreen) findPreference(USB_TETHER_SETTINGS);
+
+        ConnectivityManager cm =
+                (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
+        mUsbRegexs = cm.getTetherableUsbRegexs();
+        if (mUsbRegexs.length == 0) {
+            getPreferenceScreen().removePreference(mUsbTether);
+            getPreferenceScreen().removePreference(mEnableTetherNotice);
+        }
+        mWifiRegexs = cm.getTetherableWifiRegexs();
     }
 
+
     private class TetherChangeReceiver extends BroadcastReceiver {
         public void onReceive(Context content, Intent intent) {
-            updateState(intent.getIntExtra(ConnectivityManager.EXTRA_AVAILABLE_TETHER_COUNT,0)>0,
-                    intent.getIntExtra(ConnectivityManager.EXTRA_ACTIVE_TETHER_COUNT,0)>0);
+            // TODO - this should understand the interface types
+            ArrayList<String> available = intent.getStringArrayListExtra(
+                    ConnectivityManager.EXTRA_AVAILABLE_TETHER);
+            ArrayList<String> active = intent.getStringArrayListExtra(
+                    ConnectivityManager.EXTRA_ACTIVE_TETHER);
+
+            updateState(available, active);
         }
     }
 
@@ -68,11 +90,9 @@
 
         IntentFilter filter = new IntentFilter(ConnectivityManager.ACTION_TETHER_STATE_CHANGED);
         mTetherChangeReceiver = new TetherChangeReceiver();
-        registerReceiver(mTetherChangeReceiver, filter);
+        Intent intent = registerReceiver(mTetherChangeReceiver, filter);
 
-        ConnectivityManager cm =
-                (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
-        updateState(cm.getTetherableIfaces().length>0, cm.getTetheredIfaces().length>0);
+        if (intent != null) mTetherChangeReceiver.onReceive(this, intent);
     }
 
     @Override
@@ -82,11 +102,33 @@
         mTetherChangeReceiver = null;
     }
 
-    private void updateState(boolean isAvailable, boolean isTethered) {
-        if (isTethered) {
+    private void updateState(ArrayList<String> available, ArrayList<String> tethered) {
+        boolean usbTethered = false;
+        boolean usbAvailable = false;
+        boolean wifiTethered = false;
+        boolean wifiAvailable = false;
+
+        for (String s : available) {
+            for (String regex : mUsbRegexs) {
+                if (s.matches(regex)) usbAvailable = true;
+            }
+            for (String regex : mWifiRegexs) {
+                if (s.matches(regex)) wifiAvailable = true;
+            }
+        }
+        for (String s : tethered) {
+            for (String regex : mUsbRegexs) {
+                if (s.matches(regex)) usbTethered = true;
+            }
+            for (String regex : mWifiRegexs) {
+                if (s.matches(regex)) wifiTethered = true;
+            }
+        }
+
+        if (usbTethered) {
             mUsbTether.setSummary(R.string.usb_tethering_active_subtext);
             mUsbTether.setEnabled(true);
-        } else if (isAvailable) {
+        } else if (usbAvailable) {
             mUsbTether.setSummary(R.string.usb_tethering_available_subtext);
             mUsbTether.setEnabled(true);
         } else {