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

src/x87/builtins-x87.cc

Index: src/x87/builtins-x87.cc
diff --git a/src/x87/builtins-x87.cc b/src/x87/builtins-x87.cc
index 88733e14dc1ca75b799c94f56b89783ef02b38b9..8223f901d463013a0427e82d52114e661c60883d 100644
--- a/src/x87/builtins-x87.cc
+++ b/src/x87/builtins-x87.cc
@@ -32,6 +32,12 @@ void Builtins::Generate_Adaptor(MacroAssembler* masm,
   // -----------------------------------
   __ AssertFunction(edi);
 
+  // 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).
+  __ mov(esi, FieldOperand(edi, JSFunction::kContextOffset));
+
   // Insert extra arguments.
   int num_extra_args = 0;
   if (extra_args != BuiltinExtraArguments::kNone) {