Add plumbing for accessing latest country in variations service in Java

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivitySessionTracker.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser;
 
 import android.app.Activity;
 import android.app.Application;
 import android.content.SharedPreferences;
 import android.provider.Settings;
+import android.support.annotation.Nullable;
 import android.text.TextUtils;
 
 import org.chromium.base.ApplicationState;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.ApplicationStatus.ApplicationStateListener;
 import org.chromium.base.Callback;
 import org.chromium.base.ContextUtils;
 import org.chromium.base.LocaleUtils;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
@@ skipping 55 matching lines @@
     /**
      * Asynchronously returns the value of the "restrict" URL param that the variations service
      * should use for variation seed requests.
      * @param callback Callback that will be called with the param value when available.
      */
     public void getVariationsRestrictModeValue(Callback<String> callback) {
         mVariationsSession.getRestrictModeValue(mApplication, callback);
     }
 
     /**
+     * @return The latest country according to the current variations state. Null if not available.
+     */
+    @Nullable
+    public String getVariationsLatestCountry() {
+        return mVariationsSession.getLatestCountry();
+    }
+
+    /**
      * Handle any initialization that occurs once native has been loaded.
      */
     public void initializeWithNative() {
         ThreadUtils.assertOnUiThread();
 
         if (mIsInitialized) return;
         mIsInitialized = true;
         assert !mIsStarted;
 
         ApplicationStatus.registerApplicationStateListener(createApplicationStateListener());
@@ skipping 149 matching lines @@
     }
 
     /**
      * @return The PowerBroadcastReceiver for the browser process.
      */
     @VisibleForTesting
     public PowerBroadcastReceiver getPowerBroadcastReceiverForTesting() {
         return mPowerBroadcastReceiver;
     }
 }