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

src/arm/builtins-arm.cc

Index: src/arm/builtins-arm.cc
diff --git a/src/arm/builtins-arm.cc b/src/arm/builtins-arm.cc
index a44826813e21252d57db83c77b62888ad91dffa4..d7fc11fc3bfd84d8fe1733aed0f60409fcff068f 100644
--- a/src/arm/builtins-arm.cc
+++ b/src/arm/builtins-arm.cc
@@ -31,6 +31,12 @@ void Builtins::Generate_Adaptor(MacroAssembler* masm,
   // -----------------------------------
   __ AssertFunction(r1);
 
+  // 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(r1, JSFunction::kContextOffset));
+
   // Insert extra arguments.
   int num_extra_args = 0;
   switch (extra_args) {