[builtins] Fix context for ConstructStub calls into C++.

src/arm64/builtins-arm64.cc

 // Copyright 2013 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.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/arm64/frames-arm64.h"
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
@@ skipping 29 matching lines @@
   //  -- x0                 : number of arguments excluding receiver
   //  -- x1                 : target
   //  -- x3                 : new target
   //  -- sp[0]              : last argument
   //  -- ...
   //  -- sp[4 * (argc - 1)] : first argument
   //  -- sp[4 * argc]       : receiver
   // -----------------------------------
   __ AssertFunction(x1);
 
+  // Make sure we operate in the context of the called function (for example
+  // ConstructStubs implemented in C++ will be run in the context of the caller
+  // instead of the callee, due to the way that [[Construct]] is defined for
+  // ordinary functions).
+  __ Ldr(cp, FieldMemOperand(x1, JSFunction::kContextOffset));
+
   // Insert extra arguments.
   int num_extra_args = 0;
   switch (extra_args) {
     case BuiltinExtraArguments::kTarget:
       __ Push(x1);
       ++num_extra_args;
       break;
     case BuiltinExtraArguments::kNewTarget:
       __ Push(x3);
       ++num_extra_args;
@@ skipping 2339 matching lines @@
   }
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM