DatabaseManager::terminateDatabaseThread should handle multiple DatabaseContexts.

Source/modules/webdatabase/DatabaseManager.cpp

Index: Source/modules/webdatabase/DatabaseManager.cpp
diff --git a/Source/modules/webdatabase/DatabaseManager.cpp b/Source/modules/webdatabase/DatabaseManager.cpp
index 5854cee9cf4a0be9c8ea672247ba479677eee7cc..7156e08b446a3e68acc2320b66c6aebabd4bda4f 100644
--- a/Source/modules/webdatabase/DatabaseManager.cpp
+++ b/Source/modules/webdatabase/DatabaseManager.cpp
@@ -57,11 +57,10 @@ DatabaseManager& DatabaseManager::manager()
 void DatabaseManager::terminateDatabaseThread()
 {
     ASSERT(isMainThread());
-    if (!s_databaseManager || s_databaseManager->m_contextMap.isEmpty())
+    if (!s_databaseManager)
         return;
-    // We have at most one DatabaseContext, which is for the main thread.
-    ASSERT(s_databaseManager->m_contextMap.size() == 1);
-    (*s_databaseManager->m_contextMap.values().begin())->stopDatabases();
+    for (const Member<DatabaseContext>& context : s_databaseManager->m_contextMap.values())
+        context->stopDatabases();
 }
 
 DatabaseManager::DatabaseManager()