Sharing of SharedArrayBuffer via PostMessage transfer

Source/bindings/templates/interface.cpp

Index: Source/bindings/templates/interface.cpp
diff --git a/Source/bindings/templates/interface.cpp b/Source/bindings/templates/interface.cpp
index 0ebd759e16a7affa06a8b7eb5382636e890846a6..036bb29bb0bd14e4a811cd5485583fae2f7757b3 100644
--- a/Source/bindings/templates/interface.cpp
+++ b/Source/bindings/templates/interface.cpp
@@ -746,6 +746,28 @@ v8::Local<v8::Object> {{v8_class}}::findInstanceInPrototypeChain(v8::Local<v8::V
     return buffer.get();
 }
 
+{% elif interface_name == 'SharedArrayBuffer' %}
+{{cpp_class}}* V8SharedArrayBuffer::toImpl(v8::Local<v8::Object> object)
+{
+    ASSERT(object->IsSharedArrayBuffer());
+    v8::Local<v8::SharedArrayBuffer> v8buffer = object.As<v8::SharedArrayBuffer>();
+    if (v8buffer->IsExternal()) {
+        const WrapperTypeInfo* wrapperTypeInfo = toWrapperTypeInfo(object);
+        RELEASE_ASSERT(wrapperTypeInfo);
+        RELEASE_ASSERT(wrapperTypeInfo->ginEmbedder == gin::kEmbedderBlink);
+        return toScriptWrappable(object)->toImpl<{{cpp_class}}>();
+    }
+
+    // Transfer the ownership of the allocated memory to a SharedArrayBuffer
+    // without copying.
+    v8::SharedArrayBuffer::Contents v8Contents = v8buffer->Externalize();
+    WTF::ArrayBufferContents contents(v8Contents.Data(), v8Contents.ByteLength(), WTF::ArrayBufferContents::Shared);
+    RefPtr<{{cpp_class}}> buffer = {{cpp_class}}::create(contents);
+    buffer->associateWithWrapper(v8::Isolate::GetCurrent(), buffer->wrapperTypeInfo(), object);
+
+    return buffer.get();
+}
+
 {% elif interface_name == 'ArrayBufferView' %}
 {{cpp_class}}* V8ArrayBufferView::toImpl(v8::Local<v8::Object> object)
 {
@@ -788,7 +810,25 @@ v8::Local<v8::Object> {{v8_class}}::findInstanceInPrototypeChain(v8::Local<v8::V
         return scriptWrappable->toImpl<{{cpp_class}}>();
 
     v8::Local<v8::{{interface_name}}> v8View = object.As<v8::{{interface_name}}>();
-    RefPtr<{{cpp_class}}> typedArray = {{cpp_class}}::create(V8ArrayBuffer::toImpl(v8View->Buffer()), v8View->ByteOffset(), v8View->{% if interface_name == 'DataView' %}Byte{% endif %}Length());
+    v8::Local<v8::Object> arrayBuffer = v8View->Buffer();
+    RefPtr<{{cpp_class}}> typedArray;
+{% if interface_name == 'DataView' %}
+    if (arrayBuffer->IsArrayBuffer()) {
+        typedArray = {{cpp_class}}::create(V8ArrayBuffer::toImpl(arrayBuffer), v8View->ByteOffset(), v8View->ByteLength());
+    } else if (arrayBuffer->IsSharedArrayBuffer()) {
+        typedArray = {{cpp_class}}::create(V8SharedArrayBuffer::toImpl(arrayBuffer), v8View->ByteOffset(), v8View->ByteLength());
+    } else {
+        ASSERT_NOT_REACHED();
+    }
+{% else %}
+    if (arrayBuffer->IsArrayBuffer()) {
+        typedArray = {{cpp_class}}::create(V8ArrayBuffer::toImpl(arrayBuffer), v8View->ByteOffset(), v8View->Length());
+    } else if (arrayBuffer->IsSharedArrayBuffer()) {
+        typedArray = {{cpp_class}}::create(V8SharedArrayBuffer::toImpl(arrayBuffer), v8View->ByteOffset(), v8View->Length());
+    } else {
+        ASSERT_NOT_REACHED();
+    }
+{% endif %}
     typedArray->associateWithWrapper(v8::Isolate::GetCurrent(), typedArray->wrapperTypeInfo(), object);
 
     return typedArray->toImpl<{{cpp_class}}>();