[SyncFS] Support Delete operation on LevelDBWrapper::Iterator

chrome/browser/sync_file_system/drive_backend/leveldb_wrapper_unittest.cc

Index: chrome/browser/sync_file_system/drive_backend/leveldb_wrapper_unittest.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper_unittest.cc b/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper_unittest.cc
index 406311dd10d091c2265c804a23f169739e83eff7..c161e0cf5b1f656fff514388254368a7c8360bf8 100644
--- a/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper_unittest.cc
+++ b/chrome/browser/sync_file_system/drive_backend/leveldb_wrapper_unittest.cc
@@ -113,6 +113,21 @@ TEST_F(LevelDBWrapperTest, IteratorTest) {
 
   itr->Next();
   EXPECT_FALSE(itr->Valid());
+
+  itr->SeekToFirst();
+  EXPECT_TRUE(itr->Valid());
+  EXPECT_EQ("a", itr->key().ToString());
+  EXPECT_EQ("1", itr->value().ToString());
+
+  itr->Delete();
+  EXPECT_TRUE(itr->Valid());
+  EXPECT_EQ("ab", itr->key().ToString());
+  EXPECT_EQ("0", itr->value().ToString());
+
+  itr->SeekToFirst();
+  EXPECT_TRUE(itr->Valid());
+  EXPECT_EQ("ab", itr->key().ToString());
+  EXPECT_EQ("0", itr->value().ToString());
 }
 
 TEST_F(LevelDBWrapperTest, Iterator2Test) {