Revert 157713 - Make database failures in LeveldbValueStore more descriptive.

chrome/browser/value_store/leveldb_value_store.h

Index: chrome/browser/value_store/leveldb_value_store.h
===================================================================
--- chrome/browser/value_store/leveldb_value_store.h	(revision 157722)
+++ chrome/browser/value_store/leveldb_value_store.h	(working copy)
@@ -45,27 +45,29 @@
   // Ownership of db is taken.
   LeveldbValueStore(const FilePath& db_path, leveldb::DB* db);
 
-  // Reads a setting from the database. Returns the error message on failure,
-  // or "" on success in which case |setting| will be reset to the Value read
-  // from the database. This value may be NULL.
-  std::string ReadFromDb(
+  // Reads a setting from the database.  Returns whether the read was
+  // successful, in which case |setting| will be reset to the Value read
+  // from the database.  This value may be NULL.
+  bool ReadFromDb(
       leveldb::ReadOptions options,
       const std::string& key,
       // Will be reset() with the result, if any.
       scoped_ptr<Value>* setting);
 
-  // Adds a setting to a WriteBatch, and logs the change in |changes|. For use
-  // with WriteToDb. Returns the error message on failure, or "" on success.
-  std::string AddToBatch(
+  // Adds a setting to a WriteBatch, and logs the change in |changes|. For
+  // use with WriteToDb.
+  bool AddToBatch(
       ValueStore::WriteOptions options,
       const std::string& key,
       const base::Value& value,
       leveldb::WriteBatch* batch,
       ValueStoreChangeList* changes);
 
-  // Commits the changes in |batch| to the database, returning the error message
-  // on failure or "" on success.
-  std::string WriteToDb(leveldb::WriteBatch* batch);
+  // Commits the changes in |batch| to the database, and returns a WriteResult
+  // with the changes.
+  WriteResult WriteToDb(
+      leveldb::WriteBatch* batch,
+      scoped_ptr<ValueStoreChangeList> changes);
 
   // Returns whether the database is empty.
   bool IsEmpty();