Add a Restore() method to ValueStore and make StorageAPI use it

chrome/browser/value_store/leveldb_value_store.h

Index: chrome/browser/value_store/leveldb_value_store.h
diff --git a/chrome/browser/value_store/leveldb_value_store.h b/chrome/browser/value_store/leveldb_value_store.h
index 91217e3c7a9a799963efd6688778cd11924a0d3c..b8ddd4f0d3d06d0823a322930c497f00d85ba394 100644
--- a/chrome/browser/value_store/leveldb_value_store.h
+++ b/chrome/browser/value_store/leveldb_value_store.h
@@ -45,6 +45,12 @@ class LeveldbValueStore : public ValueStore {
   virtual WriteResult Remove(const std::string& key) OVERRIDE;
   virtual WriteResult Remove(const std::vector<std::string>& keys) OVERRIDE;
   virtual WriteResult Clear() OVERRIDE;
+  virtual bool Restore() OVERRIDE;
+  virtual bool RestoreKey(const std::string& key) OVERRIDE;
+
+  // Write directly to the backing levelDB. Only used for testing to cause
+  // corruption in the database.
+  bool WriteToDbForTest(leveldb::WriteBatch* batch);
 
  private:
   // Tries to open the database if it hasn't been opened already.