Expose v8 context a MessagePort lives in to give content side code a valid context to (de)serialize…

Source/core/dom/MessagePort.h

Index: Source/core/dom/MessagePort.h
diff --git a/Source/core/dom/MessagePort.h b/Source/core/dom/MessagePort.h
index 114e0be89512c6b3e6154c1919a9aa2229ca9ffc..200f659bd0bfb2578bfaa6b408eaf5107a6fdfd6 100644
--- a/Source/core/dom/MessagePort.h
+++ b/Source/core/dom/MessagePort.h
@@ -43,8 +43,9 @@
 namespace blink {
 
 class ExceptionState;
-class MessagePort;
 class ExecutionContext;
+class MessagePort;
+class ScriptState;
 class SerializedScriptValue;
 
 // The overwhelmingly common case is sending a single port, so handle that efficiently with an inline buffer of size 1.
@@ -112,6 +113,8 @@ private:
 
     // WebMessagePortChannelClient implementation.
     virtual void messageAvailable() override;
+    virtual v8::Isolate* scriptIsolate() override;
+    virtual v8::Local<v8::Context> scriptContextForMessageConversion() override;
     void dispatchMessages();
 
     OwnPtr<WebMessagePortChannel> m_entangledChannel;
@@ -120,6 +123,8 @@ private:
     bool m_closed;
 
     WeakPtrFactory<MessagePort> m_weakFactory;
+
+    RefPtr<ScriptState> m_scriptStateForConversion;
 };
 
 } // namespace blink