WifiNative: make getLocalLog() an instance method

We want to add some tests that mock out WifiNative.getLocalLog().
To do that, we need getLocalLog() to be an instance method.
Make it so.

While there: add @NonNull annotation to getLocalLog(), to
make the semantics clearer.

BUG=29424414
TEST=unit tests

Change-Id: Ifb224104cf54b42a945258967dcaf50541849abc
diff --git a/service/java/com/android/server/wifi/WifiMonitor.java b/service/java/com/android/server/wifi/WifiMonitor.java
index 2c1bde1..1f2b397 100644
--- a/service/java/com/android/server/wifi/WifiMonitor.java
+++ b/service/java/com/android/server/wifi/WifiMonitor.java
@@ -594,7 +594,7 @@
         while (true) {
             if (mWifiNative.connectToSupplicant()) {
                 mConnected = true;
-                new MonitorThread().start();
+                new MonitorThread(mWifiNative.getLocalLog()).start();
                 return true;
             }
             if (connectTries++ < 5) {
@@ -723,10 +723,11 @@
     }
 
     private class MonitorThread extends Thread {
-        private final LocalLog mLocalLog = mWifiNative.getLocalLog();
+        private final LocalLog mLocalLog;
 
-        public MonitorThread() {
+        public MonitorThread(LocalLog localLog) {
             super("WifiMonitor");
+            mLocalLog = localLog;
         }
 
         public void run() {
diff --git a/service/java/com/android/server/wifi/WifiNative.java b/service/java/com/android/server/wifi/WifiNative.java
index f268f62..73765ee 100644
--- a/service/java/com/android/server/wifi/WifiNative.java
+++ b/service/java/com/android/server/wifi/WifiNative.java
@@ -16,6 +16,7 @@
 
 package com.android.server.wifi;
 
+import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.app.AlarmManager;
 import android.app.PendingIntent;
@@ -104,7 +105,7 @@
 
     private static final LocalLog sLocalLog = new LocalLog(8192);
 
-    public static LocalLog getLocalLog() {
+    public @NonNull LocalLog getLocalLog() {
         return sLocalLog;
     }