Optimize the typeof operator.

src/x64/interface-descriptors-x64.cc

Index: src/x64/interface-descriptors-x64.cc
diff --git a/src/x64/interface-descriptors-x64.cc b/src/x64/interface-descriptors-x64.cc
index fe7789b1e888e3774b3793adfceddd502d8eead4..bb31cbd4063302bf6b52602c903d8d79ed5eee73 100644
--- a/src/x64/interface-descriptors-x64.cc
+++ b/src/x64/interface-descriptors-x64.cc
@@ -73,6 +73,12 @@ void FastNewContextDescriptor::Initialize(CallInterfaceDescriptorData* data) {
 }
 
 
+void TypeofDescriptor::Initialize(CallInterfaceDescriptorData* data) {
+  Register registers[] = {rsi, rbx};
+  data->Initialize(arraysize(registers), registers, NULL);
+}
+
+
 void ToNumberDescriptor::Initialize(CallInterfaceDescriptorData* data) {
   // ToNumberStub invokes a function, and therefore needs a context.
   Register registers[] = {rsi, rax};