Implement the new Photo picker, part two.

ui/android/java/src/org/chromium/ui/PhotoPickerListener.java

 // Copyright 2017 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.ui;
 
 import android.support.annotation.Nullable;
 
 import java.util.Map;
 
 /**
  * The callback used to indicate what action the user took in the picker.
  */
 public interface PhotoPickerListener {
     /**
      * The action the user took in the picker.
      */
     enum Action {
+        CANCEL,
         PHOTOS_SELECTED,
         LAUNCH_CAMERA,
         LAUNCH_GALLERY,
     }
 
     /**
      * The types of requests supported.
      */
     static final int TAKE_PHOTO_REQUEST = 1;
     static final int SHOW_GALLERY = 2;
 
     /**
      * Called when the user has selected an action. For possible actions see above.
      *
      * @param photos The photos that were selected.
      */
     void onPickerUserAction(Action action, String[] photos);
 
     /**
      * Used during testing to provide pre-canned data to the dialog.
      *
      * @return The test files to use (Map<String, Long>, mapping file paths to creation times) or
      *     null when run outside of a test.
      */
     @Nullable
     Map<String, Long> getFilesForTesting();
 }