Use v8::Context::NewRemoteContext in RemoteWindowProxy.

third_party/WebKit/Source/core/frame/RemoteFrame.h

Index: third_party/WebKit/Source/core/frame/RemoteFrame.h
diff --git a/third_party/WebKit/Source/core/frame/RemoteFrame.h b/third_party/WebKit/Source/core/frame/RemoteFrame.h
index f2fdbf8263ee678e6ae3606d691a2862d8a16cc4..3f4db59e52d611e4241be9c1874b66994501d383 100644
--- a/third_party/WebKit/Source/core/frame/RemoteFrame.h
+++ b/third_party/WebKit/Source/core/frame/RemoteFrame.h
@@ -14,6 +14,7 @@ namespace blink {
 
 class Event;
 class LocalFrame;
+class RemoteDOMWindow;
 class RemoteFrameClient;
 class RemoteFrameView;
 class WebLayer;
@@ -25,6 +26,11 @@ class CORE_EXPORT RemoteFrame final : public Frame {
 
   ~RemoteFrame() override;
 
+  // Note: this functions is not virtual but intentionally shadows the
+  // corresponding method in the Frame base class to return the
+  // RemoteFrame-specific subclass.
+  RemoteDOMWindow* domWindow() const;
+
   // Frame overrides:
   DECLARE_VIRTUAL_TRACE();
   void navigate(Document& originDocument,