[IndexedDB] Fix cursor pooling IsValid().

content/browser/indexed_db/leveldb/leveldb_iterator_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/indexed_db/leveldb/leveldb_iterator_impl.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/logging.h"
@@ skipping 20 matching lines @@
 
 leveldb::Status LevelDBIteratorImpl::CheckStatus() {
   DCHECK(!IsDetached());
   const leveldb::Status& s = iterator_->status();
   if (!s.ok())
     LOG(ERROR) << "LevelDB iterator error: " << s.ToString();
   return s;
 }
 
 bool LevelDBIteratorImpl::IsValid() const {
-  return iterator_state_ == IteratorState::EVICTED_AND_VALID ||
-         iterator_->Valid();
+  switch (iterator_state_) {
+    case IteratorState::EVICTED_AND_VALID:
+      return true;
+    case IteratorState::EVICTED_AND_INVALID:
+      return false;
+    case IteratorState::ACTIVE:
+      return iterator_->Valid();
+  }
+  NOTREACHED();
+  return false;
 }
 
 leveldb::Status LevelDBIteratorImpl::SeekToLast() {
   WillUseDBIterator();
   DCHECK(iterator_);
   iterator_->SeekToLast();
   return CheckStatus();
 }
 
 leveldb::Status LevelDBIteratorImpl::Seek(const base::StringPiece& target) {
@@ skipping 60 matching lines @@
     iterator_->Seek(key_before_eviction_);
     key_before_eviction_.clear();
     DCHECK(IsValid());
   } else {
     DCHECK(!iterator_->Valid());
   }
   iterator_state_ = IteratorState::ACTIVE;
 }
 
 }  // namespace content