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

src/mips/builtins-mips.cc

Index: src/mips/builtins-mips.cc
diff --git a/src/mips/builtins-mips.cc b/src/mips/builtins-mips.cc
index ae1b8e028661e5afa06f70b246240b66892a1a16..8cf078f89da27aa9d794f0f460f7620117553254 100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -32,6 +32,12 @@ void Builtins::Generate_Adaptor(MacroAssembler* masm,
   // -----------------------------------
   __ AssertFunction(a1);
 
+  // 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).
+  __ lw(cp, FieldMemOperand(a1, JSFunction::kContextOffset));
+
   // Insert extra arguments.
   int num_extra_args = 0;
   switch (extra_args) {