Reland "Create internal fields on global proxy objects"

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index c24445f0d94e27c50909afc111637724e60388ea..eb1f08a60942d13f71cbb7b9f0e8ab77dcb14451 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -7870,6 +7870,11 @@ class V8_EXPORT ExtensionConfiguration {
   const char** names_;
 };
 
+#ifndef V8_CONTEXT_PROXY_INTERNAL_FIELD_COUNT
+// The number of required internal fields for global proxy objects can be
+// defined by embedder.
+#define V8_CONTEXT_PROXY_INTERNAL_FIELD_COUNT 2
+#endif
 
 /**
  * A sandboxed execution context with its own set of built-in objects
@@ -8068,6 +8073,9 @@ class V8_EXPORT Context {
     Local<Context> context_;
   };
 
+  static const int kProxyInternalFieldCount =
+      V8_CONTEXT_PROXY_INTERNAL_FIELD_COUNT;
+
  private:
   friend class Value;
   friend class Script;