[IndexedDB] Adding transaction and value support to observers

content/browser/indexed_db/indexed_db_connection.cc

 // Copyright 2013 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/indexed_db_connection.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "content/browser/indexed_db/indexed_db_class_factory.h"
 #include "content/browser/indexed_db/indexed_db_database_callbacks.h"
@@ skipping 140 matching lines @@
   base::WeakPtr<IndexedDBTransaction> transaction_ptr =
       transaction->ptr_factory_.GetWeakPtr();
   transactions_[transaction->id()] = std::move(transaction);
   return transaction_ptr;
 }
 
 void IndexedDBConnection::RemoveTransaction(int64_t id) {
   transactions_.erase(id);
 }
 
+int64_t IndexedDBConnection::NextObserverTransactionId() {

[cmumford, 2017/01/09 21:31:25]

nit: "Next*" might be interpreted as a read-only operation. What do you think
about AllocObserverTransactionId()?

[dmurph, 2017/01/10 00:17:38]

NewObserverTransactionId?

+  // If we ever overflow, just reset the ID.
+  if (next_observer_transaction_id_ == kMaxObserverTransactionId) {
+    next_observer_transaction_id_ = 1ll << 32;
+  }
+  return next_observer_transaction_id_++;
+}
+
 }  // namespace content