Add a JUnit test rule for clearing app data prior to testing.

chrome/android/java_sources.gni

 # 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.
 
 import("//components/offline_pages/features/features.gni")
 
 chrome_java_sources = [
   "java/src/com/google/android/apps/chrome/appwidget/bookmarks/BookmarkThumbnailWidgetProvider.java",
   "java/src/org/chromium/chrome/browser/ActivityTabTaskDescriptionHelper.java",
   "java/src/org/chromium/chrome/browser/ActivityTaskDescriptionIconGenerator.java",
@@ skipping 1634 matching lines @@
   "javatests/src/org/chromium/chrome/browser/tabmodel/TabModelMergingTest.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/TabModelSelectorObserverTestRule.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/TabModelSelectorTabModelObserverTest.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/TabModelSelectorTabObserverTest.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/TabPersistentStoreTest.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/TabWindowManagerTest.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/TestTabModelDirectory.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/UndoTabModelTest.java",
   "javatests/src/org/chromium/chrome/browser/tabmodel/document/MockDocumentTabModel.java",
   "javatests/src/org/chromium/chrome/browser/test/ChromeBrowserTestRule.java",
+  "javatests/src/org/chromium/chrome/browser/test/ClearAppDataTestRule.java",
   "javatests/src/org/chromium/chrome/browser/toolbar/BrandColorTest.java",
   "javatests/src/org/chromium/chrome/browser/toolbar/ToolbarModelTest.java",
   "javatests/src/org/chromium/chrome/browser/toolbar/ToolbarTest.java",
   "javatests/src/org/chromium/chrome/browser/translate/TranslateCompactInfoBarTest.java",
   "javatests/src/org/chromium/chrome/browser/translate/TranslateInfoBarTest.java",
   "javatests/src/org/chromium/chrome/browser/translate/TranslateOptionsTest.java",
   "javatests/src/org/chromium/chrome/browser/util/ChromeFileProviderTest.java",
   "javatests/src/org/chromium/chrome/browser/util/FeatureUtilitiesTest.java",
   "javatests/src/org/chromium/chrome/browser/util/HashUtilTest.java",
   "javatests/src/org/chromium/chrome/browser/util/UrlUtilitiesTest.java",
@@ skipping 156 matching lines @@
   "sync_shell/javatests/src/org/chromium/chrome/browser/sync/SyncTestBase.java",
   "sync_shell/javatests/src/org/chromium/chrome/browser/sync/TypedUrlsTest.java",
   "sync_shell/javatests/src/org/chromium/chrome/browser/sync/ui/PassphraseTypeDialogFragmentTest.java",
 ]
 
 # Only used for testing, should not be shipped to end users.
 if (enable_offline_pages_harness) {
   chrome_java_sources += [ "java/src/org/chromium/chrome/browser/offlinepages/evaluation/OfflinePageEvaluationBridge.java" ]
   chrome_test_java_sources += [ "javatests/src/org/chromium/chrome/browser/offlinepages/OfflinePageSavePageLaterEvaluationTest.java" ]
 }