Accurate transfer of SerializedScriptValue allocation costs.

third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.h

 /*
  * Copyright (C) 2009, 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 121 matching lines @@
   // Informs V8 about external memory allocated and owned by this object.
   // Large values should contribute to GC counters to eventually trigger a GC,
   // otherwise flood of postMessage() can cause OOM.
   // Ok to invoke multiple times (only adds memory once).
   // The memory registration is revoked automatically in destructor.
   void registerMemoryAllocatedWithCurrentScriptContext();
 
   // Upon passing a serialized value from one context to another (via a
   // postMessage()), the allocation amounts it has registered with the
   // 'origining' context must be discharged, as the 'target' context will assume
-  // ownership of value. This method takes care of the first part of the
-  // external allocation bookkeeping, the above registration method the other
-  // half.
-  void unregisterMemoryAllocatedByCurrentScriptContext();
+  // ownership of the value. As we're potentially working across threads, this
+  // transfer of cost is handled in three stages:
+  //
+  //  - prepareForTransferringContext(): prepares and marks this
+  //    SerializedScriptValue as being destined for transfer to another
+  //    context.
+  //  - finalizeTransferringContext(): checks if the transfer was successful,
+  //    and if so, discounts allocation costs from the context just left.
+  //  - registerMemoryAllocatedWithCurrentScriptContext() - called by the
+  //    'target' once ownership has been assumed. It registers the allocation
+  //    costs of the resources that the SerializedScriptValue holds onto in
+  //    that new context.
+  //
+  // The first two are called by 'origining' context, before and after actual
+  // transfer.
+  //
+  void prepareForTransferringContext();
+  void finalizeTransferringContext();
 
   const uint8_t* data() const { return m_dataBuffer.get(); }
   size_t dataLengthInBytes() const { return m_dataBufferSize; }
 
   BlobDataHandleMap& blobDataHandles() { return m_blobDataHandles; }
   ArrayBufferContentsArray* getArrayBufferContentsArray() {
     return m_arrayBufferContentsArray.get();
   }
   ImageBitmapContentsArray* getImageBitmapContentsArray() {
     return m_imageBitmapContentsArray.get();
@@ skipping 44 matching lines @@
       v8::Local<v8::Value> value,
       ExceptionState& exceptionState) {
     return SerializedScriptValue::serialize(isolate, value, nullptr, nullptr,
                                             exceptionState);
   }
 };
 
 }  // namespace blink
 
 #endif  // SerializedScriptValue_h