Optimize the typeof operator.

src/mips/interface-descriptors-mips.cc

Index: src/mips/interface-descriptors-mips.cc
diff --git a/src/mips/interface-descriptors-mips.cc b/src/mips/interface-descriptors-mips.cc
index ec6c63f83331b6d24113df69dde813ab4e0d986b..f87c199574b363b39119aa9edf6613c95c12dcff 100644
--- a/src/mips/interface-descriptors-mips.cc
+++ b/src/mips/interface-descriptors-mips.cc
@@ -78,6 +78,12 @@ void NumberToStringDescriptor::Initialize(CallInterfaceDescriptorData* data) {
 }
 
 
+void TypeofDescriptor::Initialize(CallInterfaceDescriptorData* data) {
+  Register registers[] = {cp, a3};
+  data->Initialize(arraysize(registers), registers, NULL);
+}
+
+
 void FastCloneShallowArrayDescriptor::Initialize(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {cp, a3, a2, a1};