Revert of Move base/prefs to components/prefs

base/prefs/json_pref_store_unittest.cc

+// Copyright (c) 2012 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.
+
+#include "base/prefs/json_pref_store.h"
+
+#include <stdint.h>
+
+#include <utility>
+
+#include "base/bind.h"
+#include "base/files/file_util.h"
+#include "base/files/scoped_temp_dir.h"
+#include "base/location.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop/message_loop.h"
+#include "base/metrics/histogram_samples.h"
+#include "base/metrics/statistics_recorder.h"
+#include "base/path_service.h"
+#include "base/prefs/pref_filter.h"
+#include "base/run_loop.h"
+#include "base/single_thread_task_runner.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/test/simple_test_clock.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "base/threading/thread.h"
+#include "base/values.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace {
+
+const char kHomePage[] = "homepage";
+
+// Set the time on the given SimpleTestClock to the given time in minutes.
+void SetCurrentTimeInMinutes(double minutes, base::SimpleTestClock* clock) {
+  const int32_t kBaseTimeMins = 100;
+  clock->SetNow(base::Time::FromDoubleT((kBaseTimeMins + minutes) * 60));
+}
+
+// A PrefFilter that will intercept all calls to FilterOnLoad() and hold on
+// to the |prefs| until explicitly asked to release them.
+class InterceptingPrefFilter : public PrefFilter {
+ public:
+  InterceptingPrefFilter();
+  ~InterceptingPrefFilter() override;
+
+  // PrefFilter implementation:
+  void FilterOnLoad(
+      const PostFilterOnLoadCallback& post_filter_on_load_callback,
+      scoped_ptr<base::DictionaryValue> pref_store_contents) override;
+  void FilterUpdate(const std::string& path) override {}
+  void FilterSerializeData(
+      base::DictionaryValue* pref_store_contents) override {}
+
+  bool has_intercepted_prefs() const { return intercepted_prefs_ != NULL; }
+
+  // Finalize an intercepted read, handing |intercepted_prefs_| back to its
+  // JsonPrefStore.
+  void ReleasePrefs();
+
+ private:
+  PostFilterOnLoadCallback post_filter_on_load_callback_;
+  scoped_ptr<base::DictionaryValue> intercepted_prefs_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterceptingPrefFilter);
+};
+
+InterceptingPrefFilter::InterceptingPrefFilter() {}
+InterceptingPrefFilter::~InterceptingPrefFilter() {}
+
+void InterceptingPrefFilter::FilterOnLoad(
+    const PostFilterOnLoadCallback& post_filter_on_load_callback,
+    scoped_ptr<base::DictionaryValue> pref_store_contents) {
+  post_filter_on_load_callback_ = post_filter_on_load_callback;
+  intercepted_prefs_ = std::move(pref_store_contents);
+}
+
+void InterceptingPrefFilter::ReleasePrefs() {
+  EXPECT_FALSE(post_filter_on_load_callback_.is_null());
+  post_filter_on_load_callback_.Run(std::move(intercepted_prefs_), false);
+  post_filter_on_load_callback_.Reset();
+}
+
+class MockPrefStoreObserver : public PrefStore::Observer {
+ public:
+  MOCK_METHOD1(OnPrefValueChanged, void (const std::string&));
+  MOCK_METHOD1(OnInitializationCompleted, void (bool));
+};
+
+class MockReadErrorDelegate : public PersistentPrefStore::ReadErrorDelegate {
+ public:
+  MOCK_METHOD1(OnError, void(PersistentPrefStore::PrefReadError));
+};
+
+}  // namespace
+
+class JsonPrefStoreTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
+
+    ASSERT_TRUE(PathService::Get(base::DIR_TEST_DATA, &data_dir_));
+    data_dir_ = data_dir_.AppendASCII("prefs");
+    ASSERT_TRUE(PathExists(data_dir_));
+  }
+
+  void TearDown() override {
+    // Make sure all pending tasks have been processed (e.g., deleting the
+    // JsonPrefStore may post write tasks).
+    RunLoop().RunUntilIdle();
+  }
+
+  // The path to temporary directory used to contain the test operations.
+  base::ScopedTempDir temp_dir_;
+  // The path to the directory where the test data is stored.
+  base::FilePath data_dir_;
+  // A message loop that we can use as the file thread message loop.
+  MessageLoop message_loop_;
+
+ private:
+  // Ensure histograms are reset for each test.
+  StatisticsRecorder statistics_recorder_;
+};
+
+// Test fallback behavior for a nonexistent file.
+TEST_F(JsonPrefStoreTest, NonExistentFile) {
+  base::FilePath bogus_input_file = temp_dir_.path().AppendASCII("read.txt");
+  ASSERT_FALSE(PathExists(bogus_input_file));
+  scoped_refptr<JsonPrefStore> pref_store = new JsonPrefStore(
+      bogus_input_file, message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+  EXPECT_EQ(PersistentPrefStore::PREF_READ_ERROR_NO_FILE,
+            pref_store->ReadPrefs());
+  EXPECT_FALSE(pref_store->ReadOnly());
+}
+
+// Test fallback behavior for a nonexistent file and alternate file.
+TEST_F(JsonPrefStoreTest, NonExistentFileAndAlternateFile) {
+  base::FilePath bogus_input_file = temp_dir_.path().AppendASCII("read.txt");
+  base::FilePath bogus_alternate_input_file =
+      temp_dir_.path().AppendASCII("read_alternate.txt");
+  ASSERT_FALSE(PathExists(bogus_input_file));
+  ASSERT_FALSE(PathExists(bogus_alternate_input_file));
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(bogus_input_file, bogus_alternate_input_file,
+                        message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+  EXPECT_EQ(PersistentPrefStore::PREF_READ_ERROR_NO_FILE,
+            pref_store->ReadPrefs());
+  EXPECT_FALSE(pref_store->ReadOnly());
+}
+
+// Test fallback behavior for an invalid file.
+TEST_F(JsonPrefStoreTest, InvalidFile) {
+  base::FilePath invalid_file_original = data_dir_.AppendASCII("invalid.json");
+  base::FilePath invalid_file = temp_dir_.path().AppendASCII("invalid.json");
+  ASSERT_TRUE(base::CopyFile(invalid_file_original, invalid_file));
+  scoped_refptr<JsonPrefStore> pref_store = new JsonPrefStore(
+      invalid_file, message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+  EXPECT_EQ(PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE,
+            pref_store->ReadPrefs());
+  EXPECT_FALSE(pref_store->ReadOnly());
+
+  // The file should have been moved aside.
+  EXPECT_FALSE(PathExists(invalid_file));
+  base::FilePath moved_aside = temp_dir_.path().AppendASCII("invalid.bad");
+  EXPECT_TRUE(PathExists(moved_aside));
+  EXPECT_TRUE(TextContentsEqual(invalid_file_original, moved_aside));
+}
+
+// This function is used to avoid code duplication while testing synchronous and
+// asynchronous version of the JsonPrefStore loading.
+void RunBasicJsonPrefStoreTest(JsonPrefStore* pref_store,
+                               const base::FilePath& output_file,
+                               const base::FilePath& golden_output_file) {
+  const char kNewWindowsInTabs[] = "tabs.new_windows_in_tabs";
+  const char kMaxTabs[] = "tabs.max_tabs";
+  const char kLongIntPref[] = "long_int.pref";
+
+  std::string cnn("http://www.cnn.com");
+
+  const Value* actual;
+  EXPECT_TRUE(pref_store->GetValue(kHomePage, &actual));
+  std::string string_value;
+  EXPECT_TRUE(actual->GetAsString(&string_value));
+  EXPECT_EQ(cnn, string_value);
+
+  const char kSomeDirectory[] = "some_directory";
+
+  EXPECT_TRUE(pref_store->GetValue(kSomeDirectory, &actual));
+  base::FilePath::StringType path;
+  EXPECT_TRUE(actual->GetAsString(&path));
+  EXPECT_EQ(base::FilePath::StringType(FILE_PATH_LITERAL("/usr/local/")), path);
+  base::FilePath some_path(FILE_PATH_LITERAL("/usr/sbin/"));
+
+  pref_store->SetValue(kSomeDirectory,
+                       make_scoped_ptr(new StringValue(some_path.value())),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  EXPECT_TRUE(pref_store->GetValue(kSomeDirectory, &actual));
+  EXPECT_TRUE(actual->GetAsString(&path));
+  EXPECT_EQ(some_path.value(), path);
+
+  // Test reading some other data types from sub-dictionaries.
+  EXPECT_TRUE(pref_store->GetValue(kNewWindowsInTabs, &actual));
+  bool boolean = false;
+  EXPECT_TRUE(actual->GetAsBoolean(&boolean));
+  EXPECT_TRUE(boolean);
+
+  pref_store->SetValue(kNewWindowsInTabs,
+                       make_scoped_ptr(new FundamentalValue(false)),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  EXPECT_TRUE(pref_store->GetValue(kNewWindowsInTabs, &actual));
+  EXPECT_TRUE(actual->GetAsBoolean(&boolean));
+  EXPECT_FALSE(boolean);
+
+  EXPECT_TRUE(pref_store->GetValue(kMaxTabs, &actual));
+  int integer = 0;
+  EXPECT_TRUE(actual->GetAsInteger(&integer));
+  EXPECT_EQ(20, integer);
+  pref_store->SetValue(kMaxTabs, make_scoped_ptr(new FundamentalValue(10)),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  EXPECT_TRUE(pref_store->GetValue(kMaxTabs, &actual));
+  EXPECT_TRUE(actual->GetAsInteger(&integer));
+  EXPECT_EQ(10, integer);
+
+  pref_store->SetValue(
+      kLongIntPref,
+      make_scoped_ptr(new StringValue(base::Int64ToString(214748364842LL))),
+      WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  EXPECT_TRUE(pref_store->GetValue(kLongIntPref, &actual));
+  EXPECT_TRUE(actual->GetAsString(&string_value));
+  int64_t value;
+  base::StringToInt64(string_value, &value);
+  EXPECT_EQ(214748364842LL, value);
+
+  // Serialize and compare to expected output.
+  ASSERT_TRUE(PathExists(golden_output_file));
+  pref_store->CommitPendingWrite();
+  RunLoop().RunUntilIdle();
+  EXPECT_TRUE(TextContentsEqual(golden_output_file, output_file));
+  ASSERT_TRUE(base::DeleteFile(output_file, false));
+}
+
+TEST_F(JsonPrefStoreTest, Basic) {
+  ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
+                             temp_dir_.path().AppendASCII("write.json")));
+
+  // Test that the persistent value can be loaded.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  ASSERT_TRUE(PathExists(input_file));
+  scoped_refptr<JsonPrefStore> pref_store = new JsonPrefStore(
+      input_file, message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+  ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
+  EXPECT_FALSE(pref_store->ReadOnly());
+  EXPECT_TRUE(pref_store->IsInitializationComplete());
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, BasicAsync) {
+  ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
+                             temp_dir_.path().AppendASCII("write.json")));
+
+  // Test that the persistent value can be loaded.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  ASSERT_TRUE(PathExists(input_file));
+  scoped_refptr<JsonPrefStore> pref_store = new JsonPrefStore(
+      input_file, message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+
+  {
+    MockPrefStoreObserver mock_observer;
+    pref_store->AddObserver(&mock_observer);
+
+    MockReadErrorDelegate* mock_error_delegate = new MockReadErrorDelegate;
+    pref_store->ReadPrefsAsync(mock_error_delegate);
+
+    EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
+    EXPECT_CALL(*mock_error_delegate,
+                OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
+    RunLoop().RunUntilIdle();
+    pref_store->RemoveObserver(&mock_observer);
+
+    EXPECT_FALSE(pref_store->ReadOnly());
+    EXPECT_TRUE(pref_store->IsInitializationComplete());
+  }
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, PreserveEmptyValues) {
+  FilePath pref_file = temp_dir_.path().AppendASCII("empty_values.json");
+
+  scoped_refptr<JsonPrefStore> pref_store = new JsonPrefStore(
+      pref_file, message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+
+  // Set some keys with empty values.
+  pref_store->SetValue("list", make_scoped_ptr(new base::ListValue),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  pref_store->SetValue("dict", make_scoped_ptr(new base::DictionaryValue),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+
+  // Write to file.
+  pref_store->CommitPendingWrite();
+  RunLoop().RunUntilIdle();
+
+  // Reload.
+  pref_store = new JsonPrefStore(pref_file, message_loop_.task_runner(),
+                                 scoped_ptr<PrefFilter>());
+  ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
+  ASSERT_FALSE(pref_store->ReadOnly());
+
+  // Check values.
+  const Value* result = NULL;
+  EXPECT_TRUE(pref_store->GetValue("list", &result));
+  EXPECT_TRUE(ListValue().Equals(result));
+  EXPECT_TRUE(pref_store->GetValue("dict", &result));
+  EXPECT_TRUE(DictionaryValue().Equals(result));
+}
+
+// This test is just documenting some potentially non-obvious behavior. It
+// shouldn't be taken as normative.
+TEST_F(JsonPrefStoreTest, RemoveClearsEmptyParent) {
+  FilePath pref_file = temp_dir_.path().AppendASCII("empty_values.json");
+
+  scoped_refptr<JsonPrefStore> pref_store = new JsonPrefStore(
+      pref_file, message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+
+  scoped_ptr<base::DictionaryValue> dict(new base::DictionaryValue);
+  dict->SetString("key", "value");
+  pref_store->SetValue("dict", std::move(dict),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+
+  pref_store->RemoveValue("dict.key",
+                          WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+
+  const base::Value* retrieved_dict = NULL;
+  bool has_dict = pref_store->GetValue("dict", &retrieved_dict);
+  EXPECT_FALSE(has_dict);
+}
+
+// Tests asynchronous reading of the file when there is no file.
+TEST_F(JsonPrefStoreTest, AsyncNonExistingFile) {
+  base::FilePath bogus_input_file = temp_dir_.path().AppendASCII("read.txt");
+  ASSERT_FALSE(PathExists(bogus_input_file));
+  scoped_refptr<JsonPrefStore> pref_store = new JsonPrefStore(
+      bogus_input_file, message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+  MockPrefStoreObserver mock_observer;
+  pref_store->AddObserver(&mock_observer);
+
+  MockReadErrorDelegate *mock_error_delegate = new MockReadErrorDelegate;
+  pref_store->ReadPrefsAsync(mock_error_delegate);
+
+  EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
+  EXPECT_CALL(*mock_error_delegate,
+              OnError(PersistentPrefStore::PREF_READ_ERROR_NO_FILE)).Times(1);
+  RunLoop().RunUntilIdle();
+  pref_store->RemoveObserver(&mock_observer);
+
+  EXPECT_FALSE(pref_store->ReadOnly());
+}
+
+TEST_F(JsonPrefStoreTest, ReadWithInterceptor) {
+  ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
+                             temp_dir_.path().AppendASCII("write.json")));
+
+  // Test that the persistent value can be loaded.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  ASSERT_TRUE(PathExists(input_file));
+
+  scoped_ptr<InterceptingPrefFilter> intercepting_pref_filter(
+      new InterceptingPrefFilter());
+  InterceptingPrefFilter* raw_intercepting_pref_filter_ =
+      intercepting_pref_filter.get();
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file, message_loop_.task_runner(),
+                        std::move(intercepting_pref_filter));
+
+  ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE,
+            pref_store->ReadPrefs());
+  EXPECT_FALSE(pref_store->ReadOnly());
+
+  // The store shouldn't be considered initialized until the interceptor
+  // returns.
+  EXPECT_TRUE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+  EXPECT_FALSE(pref_store->IsInitializationComplete());
+  EXPECT_FALSE(pref_store->GetValue(kHomePage, NULL));
+
+  raw_intercepting_pref_filter_->ReleasePrefs();
+
+  EXPECT_FALSE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+  EXPECT_TRUE(pref_store->IsInitializationComplete());
+  EXPECT_TRUE(pref_store->GetValue(kHomePage, NULL));
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, ReadAsyncWithInterceptor) {
+  ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
+                             temp_dir_.path().AppendASCII("write.json")));
+
+  // Test that the persistent value can be loaded.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  ASSERT_TRUE(PathExists(input_file));
+
+  scoped_ptr<InterceptingPrefFilter> intercepting_pref_filter(
+      new InterceptingPrefFilter());
+  InterceptingPrefFilter* raw_intercepting_pref_filter_ =
+      intercepting_pref_filter.get();
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file, message_loop_.task_runner(),
+                        std::move(intercepting_pref_filter));
+
+  MockPrefStoreObserver mock_observer;
+  pref_store->AddObserver(&mock_observer);
+
+  // Ownership of the |mock_error_delegate| is handed to the |pref_store| below.
+  MockReadErrorDelegate* mock_error_delegate = new MockReadErrorDelegate;
+
+  {
+    pref_store->ReadPrefsAsync(mock_error_delegate);
+
+    EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(0);
+    // EXPECT_CALL(*mock_error_delegate,
+    //             OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
+    RunLoop().RunUntilIdle();
+
+    EXPECT_FALSE(pref_store->ReadOnly());
+    EXPECT_TRUE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+    EXPECT_FALSE(pref_store->IsInitializationComplete());
+    EXPECT_FALSE(pref_store->GetValue(kHomePage, NULL));
+  }
+
+  {
+    EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
+    // EXPECT_CALL(*mock_error_delegate,
+    //             OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
+
+    raw_intercepting_pref_filter_->ReleasePrefs();
+
+    EXPECT_FALSE(pref_store->ReadOnly());
+    EXPECT_FALSE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+    EXPECT_TRUE(pref_store->IsInitializationComplete());
+    EXPECT_TRUE(pref_store->GetValue(kHomePage, NULL));
+  }
+
+  pref_store->RemoveObserver(&mock_observer);
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, AlternateFile) {
+  ASSERT_TRUE(
+      base::CopyFile(data_dir_.AppendASCII("read.json"),
+                     temp_dir_.path().AppendASCII("alternate.json")));
+
+  // Test that the alternate file is moved to the main file and read as-is from
+  // there.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  base::FilePath alternate_input_file =
+      temp_dir_.path().AppendASCII("alternate.json");
+  ASSERT_FALSE(PathExists(input_file));
+  ASSERT_TRUE(PathExists(alternate_input_file));
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file, alternate_input_file,
+                        message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+
+  ASSERT_FALSE(PathExists(input_file));
+  ASSERT_TRUE(PathExists(alternate_input_file));
+  ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
+
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_FALSE(PathExists(alternate_input_file));
+
+  EXPECT_FALSE(pref_store->ReadOnly());
+  EXPECT_TRUE(pref_store->IsInitializationComplete());
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, AlternateFileIgnoredWhenMainFileExists) {
+  ASSERT_TRUE(
+      base::CopyFile(data_dir_.AppendASCII("read.json"),
+                     temp_dir_.path().AppendASCII("write.json")));
+  ASSERT_TRUE(
+      base::CopyFile(data_dir_.AppendASCII("invalid.json"),
+                     temp_dir_.path().AppendASCII("alternate.json")));
+
+  // Test that the alternate file is ignored and that the read occurs from the
+  // existing main file. There is no attempt at even deleting the alternate
+  // file as this scenario should never happen in normal user-data-dirs.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  base::FilePath alternate_input_file =
+      temp_dir_.path().AppendASCII("alternate.json");
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_TRUE(PathExists(alternate_input_file));
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file, alternate_input_file,
+                        message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_TRUE(PathExists(alternate_input_file));
+  ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
+
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_TRUE(PathExists(alternate_input_file));
+
+  EXPECT_FALSE(pref_store->ReadOnly());
+  EXPECT_TRUE(pref_store->IsInitializationComplete());
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, AlternateFileDNE) {
+  ASSERT_TRUE(
+      base::CopyFile(data_dir_.AppendASCII("read.json"),
+                     temp_dir_.path().AppendASCII("write.json")));
+
+  // Test that the basic read works fine when an alternate file is specified but
+  // does not exist.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  base::FilePath alternate_input_file =
+      temp_dir_.path().AppendASCII("alternate.json");
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_FALSE(PathExists(alternate_input_file));
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file, alternate_input_file,
+                        message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_FALSE(PathExists(alternate_input_file));
+  ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
+
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_FALSE(PathExists(alternate_input_file));
+
+  EXPECT_FALSE(pref_store->ReadOnly());
+  EXPECT_TRUE(pref_store->IsInitializationComplete());
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, BasicAsyncWithAlternateFile) {
+  ASSERT_TRUE(
+      base::CopyFile(data_dir_.AppendASCII("read.json"),
+                     temp_dir_.path().AppendASCII("alternate.json")));
+
+  // Test that the alternate file is moved to the main file and read as-is from
+  // there even when the read is made asynchronously.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  base::FilePath alternate_input_file =
+      temp_dir_.path().AppendASCII("alternate.json");
+  ASSERT_FALSE(PathExists(input_file));
+  ASSERT_TRUE(PathExists(alternate_input_file));
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file, alternate_input_file,
+                        message_loop_.task_runner(), scoped_ptr<PrefFilter>());
+
+  ASSERT_FALSE(PathExists(input_file));
+  ASSERT_TRUE(PathExists(alternate_input_file));
+
+  {
+    MockPrefStoreObserver mock_observer;
+    pref_store->AddObserver(&mock_observer);
+
+    MockReadErrorDelegate* mock_error_delegate = new MockReadErrorDelegate;
+    pref_store->ReadPrefsAsync(mock_error_delegate);
+
+    EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
+    EXPECT_CALL(*mock_error_delegate,
+                OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
+    RunLoop().RunUntilIdle();
+    pref_store->RemoveObserver(&mock_observer);
+
+    EXPECT_FALSE(pref_store->ReadOnly());
+    EXPECT_TRUE(pref_store->IsInitializationComplete());
+  }
+
+  ASSERT_TRUE(PathExists(input_file));
+  ASSERT_FALSE(PathExists(alternate_input_file));
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, WriteCountHistogramTestBasic) {
+  SimpleTestClock* test_clock = new SimpleTestClock;
+  SetCurrentTimeInMinutes(0, test_clock);
+  JsonPrefStore::WriteCountHistogram histogram(
+      base::TimeDelta::FromSeconds(10),
+      base::FilePath(FILE_PATH_LITERAL("/tmp/Local State")),
+      scoped_ptr<base::Clock>(test_clock));
+  int32_t report_interval =
+      JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins;
+
+  histogram.RecordWriteOccured();
+
+  SetCurrentTimeInMinutes(1.5 * report_interval, test_clock);
+  histogram.ReportOutstandingWrites();
+  scoped_ptr<HistogramSamples> samples =
+      histogram.GetHistogram()->SnapshotSamples();
+  ASSERT_EQ(1, samples->GetCount(1));
+  ASSERT_EQ(1, samples->TotalCount());
+
+  ASSERT_EQ("Settings.JsonDataWriteCount.Local_State",
+            histogram.GetHistogram()->histogram_name());
+  ASSERT_TRUE(histogram.GetHistogram()->HasConstructionArguments(1, 30, 31));
+}
+
+TEST_F(JsonPrefStoreTest, WriteCountHistogramTestSinglePeriod) {
+  SimpleTestClock* test_clock = new SimpleTestClock;
+  SetCurrentTimeInMinutes(0, test_clock);
+  JsonPrefStore::WriteCountHistogram histogram(
+      base::TimeDelta::FromSeconds(10),
+      base::FilePath(FILE_PATH_LITERAL("/tmp/Local State")),
+      scoped_ptr<base::Clock>(test_clock));
+  int32_t report_interval =
+      JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins;
+
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(0.5 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(0.7 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+
+  // Nothing should be recorded until the report period has elapsed.
+  scoped_ptr<HistogramSamples> samples =
+      histogram.GetHistogram()->SnapshotSamples();
+  ASSERT_EQ(0, samples->TotalCount());
+
+  SetCurrentTimeInMinutes(1.3 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+
+  // Now the report period has elapsed.
+  samples = histogram.GetHistogram()->SnapshotSamples();
+  ASSERT_EQ(1, samples->GetCount(3));
+  ASSERT_EQ(1, samples->TotalCount());
+
+  // The last write won't be recorded because the second count period hasn't
+  // fully elapsed.
+  SetCurrentTimeInMinutes(1.5 * report_interval, test_clock);
+  histogram.ReportOutstandingWrites();
+
+  samples = histogram.GetHistogram()->SnapshotSamples();
+  ASSERT_EQ(1, samples->GetCount(3));
+  ASSERT_EQ(1, samples->TotalCount());
+}
+
+TEST_F(JsonPrefStoreTest, WriteCountHistogramTestMultiplePeriods) {
+  SimpleTestClock* test_clock = new SimpleTestClock;
+  SetCurrentTimeInMinutes(0, test_clock);
+  JsonPrefStore::WriteCountHistogram histogram(
+      base::TimeDelta::FromSeconds(10),
+      base::FilePath(FILE_PATH_LITERAL("/tmp/Local State")),
+      scoped_ptr<base::Clock>(test_clock));
+  int32_t report_interval =
+      JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins;
+
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(0.5 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(0.7 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(1.3 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(1.5 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(2.1 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(2.5 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(2.7 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(3.3 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+
+  // The last write won't be recorded because the second count period hasn't
+  // fully elapsed
+  SetCurrentTimeInMinutes(3.5 * report_interval, test_clock);
+  histogram.ReportOutstandingWrites();
+  scoped_ptr<HistogramSamples> samples =
+      histogram.GetHistogram()->SnapshotSamples();
+  ASSERT_EQ(2, samples->GetCount(3));
+  ASSERT_EQ(1, samples->GetCount(2));
+  ASSERT_EQ(3, samples->TotalCount());
+}
+
+TEST_F(JsonPrefStoreTest, WriteCountHistogramTestPeriodWithGaps) {
+  SimpleTestClock* test_clock = new SimpleTestClock;
+  SetCurrentTimeInMinutes(0, test_clock);
+  JsonPrefStore::WriteCountHistogram histogram(
+      base::TimeDelta::FromSeconds(10),
+      base::FilePath(FILE_PATH_LITERAL("/tmp/Local State")),
+      scoped_ptr<base::Clock>(test_clock));
+  int32_t report_interval =
+      JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins;
+
+  // 1 write in the first period.
+  histogram.RecordWriteOccured();
+
+  // No writes in the second and third periods.
+
+  // 2 writes in the fourth period.
+  SetCurrentTimeInMinutes(3.1 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(3.3 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+
+  // No writes in the fifth period.
+
+  // 3 writes in the sixth period.
+  SetCurrentTimeInMinutes(5.1 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(5.3 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+  SetCurrentTimeInMinutes(5.5 * report_interval, test_clock);
+  histogram.RecordWriteOccured();
+
+  SetCurrentTimeInMinutes(6.1 * report_interval, test_clock);
+  histogram.ReportOutstandingWrites();
+  scoped_ptr<HistogramSamples> samples =
+      histogram.GetHistogram()->SnapshotSamples();
+  ASSERT_EQ(3, samples->GetCount(0));
+  ASSERT_EQ(1, samples->GetCount(1));
+  ASSERT_EQ(1, samples->GetCount(2));
+  ASSERT_EQ(1, samples->GetCount(3));
+  ASSERT_EQ(6, samples->TotalCount());
+}
+
+class JsonPrefStoreLossyWriteTest : public JsonPrefStoreTest {
+ protected:
+  void SetUp() override {
+    JsonPrefStoreTest::SetUp();
+    test_file_ = temp_dir_.path().AppendASCII("test.json");
+  }
+
+  // Creates a JsonPrefStore with the given |file_writer|.
+  scoped_refptr<JsonPrefStore> CreatePrefStore() {
+    return new JsonPrefStore(test_file_, message_loop_.task_runner(),
+                             scoped_ptr<PrefFilter>());
+  }
+
+  // Return the ImportantFileWriter for a given JsonPrefStore.
+  ImportantFileWriter* GetImportantFileWriter(
+      scoped_refptr<JsonPrefStore> pref_store) {
+    return &(pref_store->writer_);
+  }
+
+  // Get the contents of kTestFile. Pumps the message loop before returning the
+  // result.
+  std::string GetTestFileContents() {
+    RunLoop().RunUntilIdle();
+    std::string file_contents;
+    ReadFileToString(test_file_, &file_contents);
+    return file_contents;
+  }
+
+ private:
+  base::FilePath test_file_;
+};
+
+TEST_F(JsonPrefStoreLossyWriteTest, LossyWriteBasic) {
+  scoped_refptr<JsonPrefStore> pref_store = CreatePrefStore();
+  ImportantFileWriter* file_writer = GetImportantFileWriter(pref_store);
+
+  // Set a normal pref and check that it gets scheduled to be written.
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  pref_store->SetValue("normal",
+                       make_scoped_ptr(new base::StringValue("normal")),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  ASSERT_TRUE(file_writer->HasPendingWrite());
+  file_writer->DoScheduledWrite();
+  ASSERT_EQ("{\"normal\":\"normal\"}", GetTestFileContents());
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+
+  // Set a lossy pref and check that it is not scheduled to be written.
+  // SetValue/RemoveValue.
+  pref_store->SetValue("lossy", make_scoped_ptr(new base::StringValue("lossy")),
+                       WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  pref_store->RemoveValue("lossy", WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+
+  // SetValueSilently/RemoveValueSilently.
+  pref_store->SetValueSilently("lossy",
+                               make_scoped_ptr(new base::StringValue("lossy")),
+                               WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  pref_store->RemoveValueSilently("lossy",
+                                  WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+
+  // ReportValueChanged.
+  pref_store->SetValue("lossy", make_scoped_ptr(new base::StringValue("lossy")),
+                       WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  pref_store->ReportValueChanged("lossy",
+                                 WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+
+  // Call CommitPendingWrite and check that the lossy pref and the normal pref
+  // are there with the last values set above.
+  pref_store->CommitPendingWrite();
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  ASSERT_EQ("{\"lossy\":\"lossy\",\"normal\":\"normal\"}",
+            GetTestFileContents());
+}
+
+TEST_F(JsonPrefStoreLossyWriteTest, LossyWriteMixedLossyFirst) {
+  scoped_refptr<JsonPrefStore> pref_store = CreatePrefStore();
+  ImportantFileWriter* file_writer = GetImportantFileWriter(pref_store);
+
+  // Set a lossy pref and check that it is not scheduled to be written.
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  pref_store->SetValue("lossy", make_scoped_ptr(new base::StringValue("lossy")),
+                       WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+
+  // Set a normal pref and check that it is scheduled to be written.
+  pref_store->SetValue("normal",
+                       make_scoped_ptr(new base::StringValue("normal")),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  ASSERT_TRUE(file_writer->HasPendingWrite());
+
+  // Call DoScheduledWrite and check both prefs get written.
+  file_writer->DoScheduledWrite();
+  ASSERT_EQ("{\"lossy\":\"lossy\",\"normal\":\"normal\"}",
+            GetTestFileContents());
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+}
+
+TEST_F(JsonPrefStoreLossyWriteTest, LossyWriteMixedLossySecond) {
+  scoped_refptr<JsonPrefStore> pref_store = CreatePrefStore();
+  ImportantFileWriter* file_writer = GetImportantFileWriter(pref_store);
+
+  // Set a normal pref and check that it is scheduled to be written.
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  pref_store->SetValue("normal",
+                       make_scoped_ptr(new base::StringValue("normal")),
+                       WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
+  ASSERT_TRUE(file_writer->HasPendingWrite());
+
+  // Set a lossy pref and check that the write is still scheduled.
+  pref_store->SetValue("lossy", make_scoped_ptr(new base::StringValue("lossy")),
+                       WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_TRUE(file_writer->HasPendingWrite());
+
+  // Call DoScheduledWrite and check both prefs get written.
+  file_writer->DoScheduledWrite();
+  ASSERT_EQ("{\"lossy\":\"lossy\",\"normal\":\"normal\"}",
+            GetTestFileContents());
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+}
+
+TEST_F(JsonPrefStoreLossyWriteTest, ScheduleLossyWrite) {
+  scoped_refptr<JsonPrefStore> pref_store = CreatePrefStore();
+  ImportantFileWriter* file_writer = GetImportantFileWriter(pref_store);
+
+  // Set a lossy pref and check that it is not scheduled to be written.
+  pref_store->SetValue("lossy", make_scoped_ptr(new base::StringValue("lossy")),
+                       WriteablePrefStore::LOSSY_PREF_WRITE_FLAG);
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+
+  // Schedule pending lossy writes and check that it is scheduled.
+  pref_store->SchedulePendingLossyWrites();
+  ASSERT_TRUE(file_writer->HasPendingWrite());
+
+  // Call CommitPendingWrite and check that the lossy pref is there with the
+  // last value set above.
+  pref_store->CommitPendingWrite();
+  ASSERT_FALSE(file_writer->HasPendingWrite());
+  ASSERT_EQ("{\"lossy\":\"lossy\"}", GetTestFileContents());
+}
+
+}  // namespace base