PVer4: Test checksum on startup outside the hotpath of DB load

components/safe_browsing_db/v4_store.h

Index: components/safe_browsing_db/v4_store.h
diff --git a/components/safe_browsing_db/v4_store.h b/components/safe_browsing_db/v4_store.h
index f0172808c8f92d8b0df83b25a174801190c2ac8a..ed86f36dd181b6652c834e28e6aead5a84cbd069 100644
--- a/components/safe_browsing_db/v4_store.h
+++ b/components/safe_browsing_db/v4_store.h
@@ -180,8 +180,8 @@ class V4Store {
   // of the hash prefixes.
   void Initialize();
 
-  // Reset internal state and delete the backing file.
-  virtual bool Reset();
+  // Reset internal state.
+  void Reset();
 
  private:
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestReadFromEmptyFile);
@@ -246,6 +246,7 @@ class V4Store {
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestAdditionsWithRiceEncodingSucceeds);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestRemovalsWithRiceEncodingSucceeds);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestMergeUpdatesFailsChecksum);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestChecksumErrorOnStartup);
   friend class V4StoreTest;
 
   // If |prefix_size| is within expected range, and |raw_hashes_length| is a
@@ -293,8 +294,9 @@ class V4Store {
   // Merges the prefix map from the old store (|old_hash_prefix_map|) and the
   // update (additions_map) to populate the prefix map for the current store.
   // The indices in the |raw_removals| list, which may be NULL, are not merged.
-  // The SHA256 checksum of the final list of hash prefixes, in lexographically
-  // sorted order, must match |expected_checksum| (if it's not empty).
+  // The SHA256 checksum of the final list of hash prefixes, in
+  // lexicographically sorted order, must match |expected_checksum| (if it's not
+  // empty).
   ApplyUpdateResult MergeUpdate(const HashPrefixMap& old_hash_prefix_map,
                                 const HashPrefixMap& additions_map,
                                 const ::google::protobuf::RepeatedField<
@@ -335,12 +337,21 @@ class V4Store {
   // for the failure or reports success.
   StoreReadResult ReadFromDisk();
 
+  // Resets the state of the store on the IO thread.
+  void ResetOnIOThread();
+
   // Updates the |additions_map| with the additions received in the partial
   // update from the server.
   ApplyUpdateResult UpdateHashPrefixMapFromAdditions(
       const ::google::protobuf::RepeatedPtrField<ThreatEntrySet>& additions,
       HashPrefixMap* additions_map);
 
+  // Scheduled when reading the store file from disk on startup. When run, it
+  // ensures that the checksum of the hash prefixes in lexicographical sorted
+  // order matches the expected value. If not, it clears out the contents of
+  // the store.
+  void VerifyChecksumDelayed(const std::string& expected_checksum);
+
   // Writes the FULL_UPDATE |response| to disk as a V4StoreFileFormat proto.
   StoreWriteResult WriteToDisk(
       std::unique_ptr<ListUpdateResponse> response) const;