Wi-Fi network details page fixes.

- Fix NPE in WifiDetailPreferenceController#setIpText
- Add MAC address preference in the details section
- Set subnet mask and gateway preferences
- Do not show IP information preferences if no information is available
- Fix string capitalization errors
- Only show IPv4 DNS servers under "Network details" section

Bug: 36483230
Bug: 37096448
Bug: 36482499
Bug: 37165860
Test: m RunSettingsRoboTests
Change-Id: I0e3f0ccfc4a8d802b51ed6b3be81c75e384dd06f

src/com/android/settings/wifi/details/WifiNetworkDetailsFragment.java

@@ -16,6 +16,7 @@
 package com.android.settings.wifi.details;
 
 import android.content.Context;
+import android.net.ConnectivityManager;
 import android.net.wifi.WifiManager;
 import android.os.Bundle;
 import android.widget.Button;
@@ -45,13 +46,10 @@ public class WifiNetworkDetailsFragment extends DashboardFragment {
     private AccessPoint mAccessPoint;
     private Button mForgetButton;
     private WifiDetailPreferenceController mWifiDetailPreferenceController;
-    private WifiManager mWifiManager;
 
     @Override
     public void onAttach(Context context) {
         mAccessPoint = new AccessPoint(context, getArguments());
-        mWifiManager = context.getSystemService(WifiManager.class);
-
         super.onAttach(context);
     }
 
@@ -95,7 +93,8 @@ public class WifiNetworkDetailsFragment extends DashboardFragment {
                 mAccessPoint,
                 context,
                 getLifecycle(),
-                mWifiManager);
+                context.getSystemService(WifiManager.class),
+                context.getSystemService(ConnectivityManager.class));
 
         ArrayList<PreferenceController> controllers = new ArrayList(1);
         controllers.add(mWifiDetailPreferenceController);