Photo Picker dialog: Add a test.

chrome/android/java/src/org/chromium/chrome/browser/photo_picker/PhotoPickerDialog.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.chrome.browser.photo_picker;
 
 import android.content.Context;
 import android.os.Bundle;
 import android.support.v7.app.AlertDialog;
 import android.view.ViewGroup.LayoutParams;
 import android.view.WindowManager;
 
+import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.R;
 import org.chromium.ui.PhotoPickerListener;
 
 /**
  * UI for the photo chooser that shows on the Android platform as a result of
  * <input type=file accept=image > form element.
  */
 public class PhotoPickerDialog extends AlertDialog {
     // The category we're showing photos for.
     private PickerCategoryView mCategoryView;
@@ skipping 22 matching lines @@
         getWindow().setLayout(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
         getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                 WindowManager.LayoutParams.FLAG_FULLSCREEN);
     }
 
     @Override
     public void dismiss() {
         super.dismiss();
         mCategoryView.onDialogDismissed();
     }
+
+    @VisibleForTesting
+    public PickerCategoryView getCategoryViewForTesting() {
+        return mCategoryView;
+    }
 }