Optimize the typeof operator.

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index 6ce5faacf44df98d317ded079e1e2d5f2483372b..ab1517e0df6400bd7805bb2c31f8f63be3758e7a 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -25,6 +25,7 @@ class PlatformInterfaceDescriptor;
   V(FastNewContext)                           \
   V(ToNumber)                                 \
   V(NumberToString)                           \
+  V(Typeof)                                   \
   V(FastCloneShallowArray)                    \
   V(FastCloneShallowObject)                   \
   V(CreateAllocationSite)                     \
@@ -303,6 +304,12 @@ class NumberToStringDescriptor : public CallInterfaceDescriptor {
 };
 
 
+class TypeofDescriptor : public CallInterfaceDescriptor {
+ public:
+  DECLARE_DESCRIPTOR(TypeofDescriptor, CallInterfaceDescriptor)
+};
+
+
 class FastCloneShallowArrayDescriptor : public CallInterfaceDescriptor {
  public:
   DECLARE_DESCRIPTOR(FastCloneShallowArrayDescriptor, CallInterfaceDescriptor)