[SyncFS] Support Delete operation on LevelDBWrapper::Iterator

chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc

Index: chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc b/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc
index 3200b302366b4691d26c7741a93fb6deea69d4be..77b1461aacb9eb53f7a26a5b1cdc5ab454660a49 100644
--- a/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc
+++ b/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc
@@ -67,6 +67,20 @@ void LevelDBWrapper::Iterator::Next() {
   AdvanceIterators();
 }
 
+void LevelDBWrapper::Iterator::Delete() {
+  DCHECK(Valid());
+
+  const std::string key_str = key().ToString();
+  Transaction deletion(DELETE_OPERATION, std::string());
+  std::pair<PendingOperationMap::iterator, bool> inserted =
+      db_->pending_.insert(std::make_pair(key_str, deletion));

[tzik, 2014/08/12 06:28:33]

Can we put previous iterator as a hint like this?
insert(map_iterator_, std::make_pair(...))

[peria, 2014/08/12 06:41:48]

We can, but if we can add a hint, insert() returns an iterator, not a pair.
We need a pair to detect the element is newly added or not,
so we cannot use the hint.
http://www.cplusplus.com/reference/map/map/insert/

[tzik, 2014/08/12 07:32:36]

Ah, I wasn't aware that.
How about doing like below?
map_iterator_ = insert(map_iterator, std::make_pair(...));
map_iterator_->second = Transaction();

[peria, 2014/08/12 07:44:35]

Done.

+  map_iterator_ = inserted.first;
+  if (!inserted.second)
+    map_iterator_->second = deletion;
+
+  AdvanceIterators();
+}
+
 leveldb::Slice LevelDBWrapper::Iterator::key() {
   DCHECK(Valid());