Make OffscreenCanvas Transferable

third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h

Index: third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h
diff --git a/third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h b/third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h
new file mode 100644
index 0000000000000000000000000000000000000000..a7a96f9ff22d5eca02d1634118afb231f31ec0a6
--- /dev/null
+++ b/third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h
@@ -0,0 +1,37 @@
+// Copyright 2016 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.
+
+#ifndef TransferableOffscreenCanvasExtractor_h
+#define TransferableOffscreenCanvasExtractor_h
+
+#include "bindings/core/v8/TransferableExtractor.h"
+#include "bindings/modules/v8/TransferableOffscreenCanvas.h"
+#include "bindings/modules/v8/V8OffscreenCanvas.h"
+#include "modules/ModulesExport.h"
+#include "modules/offscreencanvas/OffscreenCanvas.h"
+
+namespace blink {
+
+class MODULES_EXPORT TransferableOffscreenCanvasExtractor : public TransferableExtractor {
+public:
+    ~TransferableOffscreenCanvasExtractor() override { }
+    bool extract(v8::Local<v8::Value> transferrable, v8::Isolate* isolate, TransferableArray& transferables, ExceptionState& exceptionState, const unsigned i) override
+    {
+        if (V8OffscreenCanvas::hasInstance(transferrable, isolate)) {
+            OffscreenCanvas* offscreenCanvas = V8OffscreenCanvas::toImpl(v8::Local<v8::Object>::Cast(transferrable));
+            TransferableOffscreenCanvas* offscreenCanvases = TransferableOffscreenCanvas::ensure(transferables);
+            if (offscreenCanvases->contains(offscreenCanvas)) {
+                exceptionState.throwDOMException(DataCloneError, "OffscreenCanvas at index " + String::number(i) + " is a duplicate of an earlier OffscreenCanvas.");
+                return false;
+            }
+            offscreenCanvases->append(offscreenCanvas);
+            return true;
+        }
+        return false;
+    }
+};
+
+} // namespace blink
+
+#endif // TransferableOffscreenCanvasExtractor_h