DCHECK for null pointers

This should help mmke it clear that you can't pass null
for keys_to_remove.

Change-Id: I63a86d6253cdd3b0e609942edf306ccd88b47a9c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2148058Reviewed-by: ssid <ssid@chromium.org>
Commit-Queue: Dan H <harringtond@chromium.org>
Cr-Commit-Position: refs/heads/master@{#761022}

components/leveldb_proto/internal/proto_leveldb_wrapper.cc

@@ -109,6 +109,8 @@ bool UpdateEntriesFromTaskRunner(
     std::unique_ptr<KeyValueVector> entries_to_save,
     std::unique_ptr<KeyVector> keys_to_remove,
     const std::string& client_id) {
+  DCHECK(entries_to_save);
+  DCHECK(keys_to_remove);
   leveldb::Status status;
   bool success = database->Save(*entries_to_save, *keys_to_remove, &status);
   ProtoLevelDBWrapperMetrics::RecordUpdate(client_id, success, status);
@@ -121,6 +123,7 @@ bool UpdateEntriesWithRemoveFilterFromTaskRunner(
     const KeyFilter& delete_key_filter,
     const std::string& target_prefix,
     const std::string& client_id) {
+  DCHECK(entries_to_save);
   leveldb::Status status;
   bool success = database->UpdateWithRemoveFilter(
       *entries_to_save, delete_key_filter, target_prefix, &status);

components/leveldb_proto/public/proto_database.h

@@ -123,7 +123,8 @@ class ProtoDatabase {
 
   // Asynchronously saves |entries_to_save| and deletes entries from
   // |keys_to_remove| from the database. |callback| will be invoked on the
-  // calling thread when complete.
+  // calling thread when complete. |entries_to_save| and |keys_to_remove| must
+  // be non-null.
   virtual void UpdateEntries(
       std::unique_ptr<typename Util::Internal<T>::KeyEntryVector>
           entries_to_save,
@@ -133,7 +134,7 @@ class ProtoDatabase {
   // Asynchronously saves |entries_to_save| and deletes entries that satisfies
   // the |delete_key_filter| from the database. |callback| will be invoked on
   // the calling thread when complete. The filter will be called on
-  // ProtoDatabase's taskrunner.
+  // ProtoDatabase's taskrunner. |entries_to_save| must be non-null.
   virtual void UpdateEntriesWithRemoveFilter(
       std::unique_ptr<typename Util::Internal<T>::KeyEntryVector>
           entries_to_save,