Revert of Move base/prefs to components/prefs

base/prefs/json_pref_store.h

Index: base/prefs/json_pref_store.h
diff --git a/base/prefs/json_pref_store.h b/base/prefs/json_pref_store.h
index 247102f1bbb2eaed95f0080e37423161ac94d6fd..6342977f9ba2ab333b1d17e8aec82116840dc9bd 100644
--- a/base/prefs/json_pref_store.h
+++ b/base/prefs/json_pref_store.h
@@ -2,6 +2,228 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// TODO(brettw) remove this forwarding header when prefs is completely moved to
-// components.
-#include "components/prefs/json_pref_store.h"
+#ifndef BASE_PREFS_JSON_PREF_STORE_H_
+#define BASE_PREFS_JSON_PREF_STORE_H_
+
+#include <stdint.h>
+
+#include <set>
+#include <string>
+
+#include "base/callback_forward.h"
+#include "base/compiler_specific.h"
+#include "base/files/file_path.h"
+#include "base/files/important_file_writer.h"
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "base/prefs/base_prefs_export.h"
+#include "base/prefs/persistent_pref_store.h"
+#include "base/threading/non_thread_safe.h"
+
+class PrefFilter;
+
+namespace base {
+class Clock;
+class DictionaryValue;
+class FilePath;
+class HistogramBase;
+class JsonPrefStoreLossyWriteTest;
+class SequencedTaskRunner;
+class SequencedWorkerPool;
+class Value;
+FORWARD_DECLARE_TEST(JsonPrefStoreTest, WriteCountHistogramTestBasic);
+FORWARD_DECLARE_TEST(JsonPrefStoreTest, WriteCountHistogramTestSinglePeriod);
+FORWARD_DECLARE_TEST(JsonPrefStoreTest, WriteCountHistogramTestMultiplePeriods);
+FORWARD_DECLARE_TEST(JsonPrefStoreTest, WriteCountHistogramTestPeriodWithGaps);
+}
+
+// A writable PrefStore implementation that is used for user preferences.
+class BASE_PREFS_EXPORT JsonPrefStore
+    : public PersistentPrefStore,
+      public base::ImportantFileWriter::DataSerializer,
+      public base::SupportsWeakPtr<JsonPrefStore>,
+      public base::NonThreadSafe {
+ public:
+  struct ReadResult;
+
+  // Returns instance of SequencedTaskRunner which guarantees that file
+  // operations on the same file will be executed in sequenced order.
+  static scoped_refptr<base::SequencedTaskRunner> GetTaskRunnerForFile(
+      const base::FilePath& pref_filename,
+      base::SequencedWorkerPool* worker_pool);
+
+  // Same as the constructor below with no alternate filename.
+  JsonPrefStore(
+      const base::FilePath& pref_filename,
+      const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
+      scoped_ptr<PrefFilter> pref_filter);
+
+  // |sequenced_task_runner| must be a shutdown-blocking task runner, ideally
+  // created by the GetTaskRunnerForFile() method above.
+  // |pref_filename| is the path to the file to read prefs from.
+  // |pref_alternate_filename| is the path to an alternate file which the
+  // desired prefs may have previously been written to. If |pref_filename|
+  // doesn't exist and |pref_alternate_filename| does, |pref_alternate_filename|
+  // will be moved to |pref_filename| before the read occurs.
+  JsonPrefStore(
+      const base::FilePath& pref_filename,
+      const base::FilePath& pref_alternate_filename,
+      const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
+      scoped_ptr<PrefFilter> pref_filter);
+
+  // PrefStore overrides:
+  bool GetValue(const std::string& key,
+                const base::Value** result) const override;
+  void AddObserver(PrefStore::Observer* observer) override;
+  void RemoveObserver(PrefStore::Observer* observer) override;
+  bool HasObservers() const override;
+  bool IsInitializationComplete() const override;
+
+  // PersistentPrefStore overrides:
+  bool GetMutableValue(const std::string& key, base::Value** result) override;
+  void SetValue(const std::string& key,
+                scoped_ptr<base::Value> value,
+                uint32_t flags) override;
+  void SetValueSilently(const std::string& key,
+                        scoped_ptr<base::Value> value,
+                        uint32_t flags) override;
+  void RemoveValue(const std::string& key, uint32_t flags) override;
+  bool ReadOnly() const override;
+  PrefReadError GetReadError() const override;
+  // Note this method may be asynchronous if this instance has a |pref_filter_|
+  // in which case it will return PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE.
+  // See details in pref_filter.h.
+  PrefReadError ReadPrefs() override;
+  void ReadPrefsAsync(ReadErrorDelegate* error_delegate) override;
+  void CommitPendingWrite() override;
+  void SchedulePendingLossyWrites() override;
+  void ReportValueChanged(const std::string& key, uint32_t flags) override;
+
+  // Just like RemoveValue(), but doesn't notify observers. Used when doing some
+  // cleanup that shouldn't otherwise alert observers.
+  void RemoveValueSilently(const std::string& key, uint32_t flags);
+
+  // Registers |on_next_successful_write| to be called once, on the next
+  // successful write event of |writer_|.
+  void RegisterOnNextSuccessfulWriteCallback(
+      const base::Closure& on_next_successful_write);
+
+ private:
+  // Represents a histogram for recording the number of writes to the pref file
+  // that occur every kHistogramWriteReportIntervalInMins minutes.
+  class BASE_PREFS_EXPORT WriteCountHistogram {
+   public:
+    static const int32_t kHistogramWriteReportIntervalMins;
+
+    WriteCountHistogram(const base::TimeDelta& commit_interval,
+                        const base::FilePath& path);
+    // Constructor for testing. |clock| is a test Clock that is used to retrieve
+    // the time.
+    WriteCountHistogram(const base::TimeDelta& commit_interval,
+                        const base::FilePath& path,
+                        scoped_ptr<base::Clock> clock);
+    ~WriteCountHistogram();
+
+    // Record that a write has occured.
+    void RecordWriteOccured();
+
+    // Reports writes (that have not yet been reported) in all of the recorded
+    // intervals that have elapsed up until current time.
+    void ReportOutstandingWrites();
+
+    base::HistogramBase* GetHistogram();
+
+   private:
+    // The minimum interval at which writes can occur.
+    const base::TimeDelta commit_interval_;
+
+    // The path to the file.
+    const base::FilePath path_;
+
+    // Clock which is used to retrieve the current time.
+    scoped_ptr<base::Clock> clock_;
+
+    // The interval at which to report write counts.
+    const base::TimeDelta report_interval_;
+
+    // The time at which the last histogram value was reported for the number
+    // of write counts.
+    base::Time last_report_time_;
+
+    // The number of writes that have occured since the last write count was
+    // reported.
+    uint32_t writes_since_last_report_;
+
+    DISALLOW_COPY_AND_ASSIGN(WriteCountHistogram);
+  };
+
+  FRIEND_TEST_ALL_PREFIXES(base::JsonPrefStoreTest,
+                           WriteCountHistogramTestBasic);
+  FRIEND_TEST_ALL_PREFIXES(base::JsonPrefStoreTest,
+                           WriteCountHistogramTestSinglePeriod);
+  FRIEND_TEST_ALL_PREFIXES(base::JsonPrefStoreTest,
+                           WriteCountHistogramTestMultiplePeriods);
+  FRIEND_TEST_ALL_PREFIXES(base::JsonPrefStoreTest,
+                           WriteCountHistogramTestPeriodWithGaps);
+  friend class base::JsonPrefStoreLossyWriteTest;
+
+  ~JsonPrefStore() override;
+
+  // This method is called after the JSON file has been read.  It then hands
+  // |value| (or an empty dictionary in some read error cases) to the
+  // |pref_filter| if one is set. It also gives a callback pointing at
+  // FinalizeFileRead() to that |pref_filter_| which is then responsible for
+  // invoking it when done. If there is no |pref_filter_|, FinalizeFileRead()
+  // is invoked directly.
+  void OnFileRead(scoped_ptr<ReadResult> read_result);
+
+  // ImportantFileWriter::DataSerializer overrides:
+  bool SerializeData(std::string* output) override;
+
+  // This method is called after the JSON file has been read and the result has
+  // potentially been intercepted and modified by |pref_filter_|.
+  // |initialization_successful| is pre-determined by OnFileRead() and should
+  // be used when reporting OnInitializationCompleted().
+  // |schedule_write| indicates whether a write should be immediately scheduled
+  // (typically because the |pref_filter_| has already altered the |prefs|) --
+  // this will be ignored if this store is read-only.
+  void FinalizeFileRead(bool initialization_successful,
+                        scoped_ptr<base::DictionaryValue> prefs,
+                        bool schedule_write);
+
+  // Schedule a write with the file writer as long as |flags| doesn't contain
+  // WriteablePrefStore::LOSSY_PREF_WRITE_FLAG.
+  void ScheduleWrite(uint32_t flags);
+
+  const base::FilePath path_;
+  const base::FilePath alternate_path_;
+  const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
+
+  scoped_ptr<base::DictionaryValue> prefs_;
+
+  bool read_only_;
+
+  // Helper for safely writing pref data.
+  base::ImportantFileWriter writer_;
+
+  scoped_ptr<PrefFilter> pref_filter_;
+  base::ObserverList<PrefStore::Observer, true> observers_;
+
+  scoped_ptr<ReadErrorDelegate> error_delegate_;
+
+  bool initialized_;
+  bool filtering_in_progress_;
+  bool pending_lossy_write_;
+  PrefReadError read_error_;
+
+  std::set<std::string> keys_need_empty_value_;
+
+  WriteCountHistogram write_count_histogram_;
+
+  DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
+};
+
+#endif  // BASE_PREFS_JSON_PREF_STORE_H_