[IndexedDB] Adding transaction and value support to observers

content/browser/indexed_db/indexed_db_connection.cc

Index: content/browser/indexed_db/indexed_db_connection.cc
diff --git a/content/browser/indexed_db/indexed_db_connection.cc b/content/browser/indexed_db/indexed_db_connection.cc
index 216786a1d365f783f207895b0158fbce7808eab7..70c3de7dd0a04251db93aa717e4a5bd3d05a0db2 100644
--- a/content/browser/indexed_db/indexed_db_connection.cc
+++ b/content/browser/indexed_db/indexed_db_connection.cc
@@ -15,7 +15,7 @@
 namespace content {
 
 namespace {
-
+static const int64_t kMaxObserverTransactionId = -1ll;
 static int32_t next_id;
 
 }  // namespace
@@ -158,4 +158,12 @@ void IndexedDBConnection::RemoveTransaction(int64_t id) {
   transactions_.erase(id);
 }
 
+int64_t IndexedDBConnection::NewObserverTransactionId() {
+  // If we ever overflow, just reset the ID.

[jsbell, 2017/01/13 00:14:12]

At 1000 transaction/sec that's 285000 years. But good to be safe. :)

[dmurph, 2017/01/13 01:50:42]

haha sgtm.

+  if (next_observer_transaction_id_ == kMaxObserverTransactionId) {

[jsbell, 2017/01/13 00:14:12]

nit: no need for {}

[dmurph, 2017/01/13 01:50:42]

Done.

+    next_observer_transaction_id_ = 1ll << 32;
+  }
+  return next_observer_transaction_id_++;

[jsbell, 2017/01/13 00:14:12]

Maybe DCHECK that the high bits are not 0 ?

(which is the critical thing here)

[dmurph, 2017/01/13 01:50:42]

Done.

+}
+
 }  // namespace content