Wrap large IndexedDB values into Blobs before writing to LevelDB.

third_party/WebKit/Source/modules/indexeddb/IDBTransaction.h

Index: third_party/WebKit/Source/modules/indexeddb/IDBTransaction.h
diff --git a/third_party/WebKit/Source/modules/indexeddb/IDBTransaction.h b/third_party/WebKit/Source/modules/indexeddb/IDBTransaction.h
index 0f5eaed372837c3acdeac43dc18a3ffc5811ac60..d620925091e117ad18e6fc3e565a022264e155ee 100644
--- a/third_party/WebKit/Source/modules/indexeddb/IDBTransaction.h
+++ b/third_party/WebKit/Source/modules/indexeddb/IDBTransaction.h
@@ -26,6 +26,8 @@
 #ifndef IDBTransaction_h
 #define IDBTransaction_h
 
+#include <memory>
+
 #include "core/dom/ContextLifecycleObserver.h"
 #include "core/dom/DOMStringList.h"
 #include "core/events/EventListener.h"
@@ -36,6 +38,7 @@
 #include "modules/indexeddb/IndexedDB.h"
 #include "platform/bindings/ActiveScriptWrappable.h"
 #include "platform/heap/Handle.h"
+#include "platform/wtf/Deque.h"
 #include "platform/wtf/HashSet.h"
 #include "platform/wtf/Vector.h"
 #include "public/platform/modules/indexeddb/WebIDBDatabase.h"
@@ -51,6 +54,7 @@ class IDBIndex;
 class IDBObjectStore;
 class IDBOpenDBRequest;
 class IDBRequest;
+class IDBRequestQueueItem;
 class ScriptState;
 
 class MODULES_EXPORT IDBTransaction final
@@ -105,6 +109,15 @@ class MODULES_EXPORT IDBTransaction final
   void RegisterRequest(IDBRequest*);
   void UnregisterRequest(IDBRequest*);
 
+  // True if this transaction has at least one request whose result is being
+  // post-processed.
+  //
+  // While this is true, new results must be queued using EnqueueResult().
+  inline bool HasQueuedResults() const { return !result_queue_.empty(); }
+  void EnqueueResult(std::unique_ptr<IDBRequestQueueItem> result);
+  // Called when a result's post-processing has completed.
+  void OnResultReady();
+
   // The methods below are called right before the changes are applied to the
   // database's metadata. We use this unusual sequencing because some of the
   // methods below need to access the metadata values before the change, and
@@ -212,6 +225,14 @@ class MODULES_EXPORT IDBTransaction final
 
   HeapListHashSet<Member<IDBRequest>> request_list_;
 
+  // The IDBRequest results whose events have not been enqueued yet.
+  //
+  // When a result requires post-processing, such as large value unwrapping, all
+  // the results that arrive during the post-processing phase are queued up.

[jsbell, 2017/05/22 21:54:20]

nit: The first result requiring post-processing is also added to the queue, so
"results that arrive during the post-processing phase..." is not quite correct,
is it?

[pwnall, 2017/05/25 13:27:12]

Done.

+  // This guarantees that result events are fired in the order in which the
+  // requests were performed, as prescribed by the IndexedDB specification.
+  Deque<std::unique_ptr<IDBRequestQueueItem>> result_queue_;
+
 #if DCHECK_IS_ON()
   bool finish_called_ = false;
 #endif  // DCHECK_IS_ON()