[IndexedDB] Fix cursor pooling IsValid().

content/browser/indexed_db/leveldb/leveldb_iterator_impl.cc

Index: content/browser/indexed_db/leveldb/leveldb_iterator_impl.cc
diff --git a/content/browser/indexed_db/leveldb/leveldb_iterator_impl.cc b/content/browser/indexed_db/leveldb/leveldb_iterator_impl.cc
index b94a3d6150bee704eba43cefa3224682b9e08f60..fe2982b6632aa84c6253cbbcd12c88b4c2f3e3a0 100644
--- a/content/browser/indexed_db/leveldb/leveldb_iterator_impl.cc
+++ b/content/browser/indexed_db/leveldb/leveldb_iterator_impl.cc
@@ -38,8 +38,18 @@ leveldb::Status LevelDBIteratorImpl::CheckStatus() {
 }
 
 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:
+      DCHECK(iterator_);

[cmumford, 2017/03/29 17:00:20]

nit: Suggest removing the DCHECK because the program will crash on the next
line, and the cause will be obvious. Don't think this adds anything of value.

[dmurph, 2017/03/29 18:07:17]

Done.

+      return iterator_->Valid();
+    default:
+      NOTREACHED();

[cmumford, 2017/03/29 17:00:20]

Remove the default because the compile will fail if not all enumeration values
are handled.

[dmurph, 2017/03/29 18:07:17]

Done.

+      return false;
+  }
 }
 
 leveldb::Status LevelDBIteratorImpl::SeekToLast() {