Implement lossy pref behavior for JsonPrefStore.

base/prefs/json_pref_store.h

 // 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.
 
 #ifndef BASE_PREFS_JSON_PREF_STORE_H_
 #define BASE_PREFS_JSON_PREF_STORE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 11 matching lines @@
 #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.
@@ skipping 116 matching lines @@
   };
 
   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 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_;
   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_