[SyncFS] Introduce counters in LevelDBWrapper

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 36569cb880bdaa98719321c4ecd6b10cfa80618c..29a54a6567ac79fdb7e180560412d12d186ad52d 100644
--- a/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc
+++ b/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.cc
@@ -78,6 +78,8 @@ void LevelDBWrapper::Iterator::Delete() {
   // update the value.
   map_iterator_->second = deletion;
 
+  ++(db_->num_deletes_);
+
   AdvanceIterators();
 }
 
@@ -142,19 +144,20 @@ void LevelDBWrapper::Iterator::AdvanceIterators() {
 // LevelDBWrapper class
 // ---------------------------------------------------------------------------
 LevelDBWrapper::LevelDBWrapper(scoped_ptr<leveldb::DB> db)
-    : db_(db.Pass()) {
+    : db_(db.Pass()), num_puts_(0), num_deletes_(0) {
   DCHECK(db_);
 }
 
 LevelDBWrapper::~LevelDBWrapper() {}
 
-void LevelDBWrapper::Put(const std::string& key,
-                         const std::string& value) {
+void LevelDBWrapper::Put(const std::string& key, const std::string& value) {
   pending_[key] = Transaction(PUT_OPERATION, value);
+  ++num_puts_;
 }
 
 void LevelDBWrapper::Delete(const std::string& key) {
   pending_[key] = Transaction(DELETE_OPERATION, std::string());
+  ++num_deletes_;
 }
 
 leveldb::Status LevelDBWrapper::Get(const std::string& key,
@@ -205,6 +208,8 @@ leveldb::Status LevelDBWrapper::Commit() {
 
 void LevelDBWrapper::Clear() {
   pending_.clear();
+  num_puts_ = 0;
+  num_deletes_ = 0;
 }
 
 leveldb::DB* LevelDBWrapper::GetLevelDB() {