Android Chromoting: Add hooks for the official account-switcher

remoting/android/java/src/org/chromium/chromoting/accountswitcher/AccountSwitcherFactory.java

 // Copyright 2015 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.chromoting.accountswitcher;
 
-import android.content.Context;
+import android.app.Activity;
 
 /**
  * Factory class for creating AccountSwitcher implementations. This enables official builds of
  * the project to implement an alternative account-switching UI.
  */
 public class AccountSwitcherFactory {
     /**
      * The singleton instance of this class. This is provided by the Application context, so that
      * different application builds can provide different implementations. It has to be
      * dependency-injected, because the Application context is defined in a higher-level build
      * target that depends on this code.
      */
     private static AccountSwitcherFactory sInstance;
 
     /** Returns the instance. Should be called on the main thread. */
     public static AccountSwitcherFactory getInstance() {
         return sInstance;
     }
 
     /**
      * Factory method to create an AccountSwitcher. This method returns the public implementation,
      * but it can be overridden to provide an alternative account-switcher implementation. This is
      * called during the Activity's onCreate() handler.
-     * @param context Context used for UI operations.
+     * @param activity Activity used for UI operations.
      * @param callback Callback for receiving notifications from the account-switcher.
      */
-    public AccountSwitcher createAccountSwitcher(Context context,
+    public AccountSwitcher createAccountSwitcher(Activity activity,
             AccountSwitcher.Callback callback) {
-        return new AccountSwitcherBasic(context, callback);
+        return new AccountSwitcherBasic(activity, callback);
     }
 
     /**
      * Sets the global instance. Called by the Application context during initialization before any
      * Activity is created.
      */
     public static void setInstance(AccountSwitcherFactory instance) {
         sInstance = instance;
     }
 }