Revert "Sysui/WifiTracker: Changes to support late starting wifi service"

This reverts commit e01f30b6bf5a850f1f11f56e108d38a2fa7451f1.

Reason for revert: Wifi services no longer plan to be a separate
APK/process for mainline. Will instead become a jar loaded from Apex.

Bug: 144722612
Test: Device boots up & connects to wifi networks.
Change-Id: Iad48a59ff397ba61fac77a4c3c296190b7c70ee5
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/policy/WifiSignalController.java b/packages/SystemUI/src/com/android/systemui/statusbar/policy/WifiSignalController.java
index 5a43321..e7d1c95 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/policy/WifiSignalController.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/policy/WifiSignalController.java
@@ -38,7 +38,6 @@
 public class WifiSignalController extends
         SignalController<WifiSignalController.WifiState, SignalController.IconGroup> {
     private final boolean mHasMobileData;
-    private final WifiManager mWifiManager;
     private final WifiStatusTracker mWifiTracker;
 
     public WifiSignalController(Context context, boolean hasMobileData,
@@ -50,11 +49,13 @@
                 context.getSystemService(NetworkScoreManager.class);
         ConnectivityManager connectivityManager =
                 context.getSystemService(ConnectivityManager.class);
-        mWifiManager = wifiManager;
         mWifiTracker = new WifiStatusTracker(mContext, wifiManager, networkScoreManager,
                 connectivityManager, this::handleStatusUpdated);
         mWifiTracker.setListening(true);
         mHasMobileData = hasMobileData;
+        if (wifiManager != null) {
+            wifiManager.registerTrafficStateCallback(new WifiTrafficStateCallback());
+        }
         // WiFi only has one state.
         mCurrentState.iconGroup = mLastState.iconGroup = new IconGroup(
                 "Wi-Fi Icons",
@@ -127,10 +128,6 @@
         notifyListenersIfNecessary();
     }
 
-    public void handleBootCompleted() {
-        mWifiManager.registerTrafficStateCallback(new WifiTrafficStateCallback());
-    }
-
     /**
      * Handler to receive the data activity on wifi.
      */