[runtime] [proxy] Adding [[SetPrototypeOf]] trap.

src/objects.h

 // Copyright 2012 the V8 project 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 V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 9481 matching lines @@
 
   static MaybeHandle<Context> GetFunctionRealm(Handle<JSProxy> proxy);
 
   DECLARE_CAST(JSProxy)
 
   bool IsRevoked();
 
   // ES6 9.5.1
   static MaybeHandle<Object> GetPrototype(Handle<JSProxy> receiver);
 
+  // ES6 9.5.2
+  MUST_USE_RESULT static Maybe<bool> SetPrototype(Handle<JSProxy> proxy,
+                                                  Handle<Object> value,
+                                                  bool from_javascript,
+                                                  ShouldThrow should_throw);
   // ES6 9.5.3
   MUST_USE_RESULT static Maybe<bool> IsExtensible(Handle<JSProxy> proxy);
 
   // ES6 9.5.4 (when passed DONT_THROW)
   MUST_USE_RESULT static Maybe<bool> PreventExtensions(
       Handle<JSProxy> proxy, ShouldThrow should_throw);
 
   // ES6 9.5.5
   static bool GetOwnPropertyDescriptor(LookupIterator* it,
                                        PropertyDescriptor* desc);
@@ skipping 1199 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_