[turbofan] Assign proper type to %ClassOf/%_ClassOf.

src/compiler/typer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/typer.h"
 
 #include <iomanip>
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
@@ skipping 1543 matching lines @@
     case Runtime::kInlineToInteger:
       return TypeUnaryOp(node, ToInteger);
     case Runtime::kInlineToLength:
       return TypeUnaryOp(node, ToLength);
     case Runtime::kInlineToNumber:
       return TypeUnaryOp(node, ToNumber);
     case Runtime::kInlineToObject:
       return TypeUnaryOp(node, ToObject);
     case Runtime::kInlineToString:
       return TypeUnaryOp(node, ToString);
+    case Runtime::kClassOf:
+    case Runtime::kInlineClassOf:
+      return Type::Union(Type::InternalizedString(), Type::Null(), zone());
     case Runtime::kHasInPrototypeChain:
       return Type::Boolean();
     default:
       break;
   }
   // TODO(turbofan): This should be Type::NonInternal(), but unfortunately we
   // have a few weird runtime calls that return the hole or even FixedArrays;
   // change this once those weird runtime calls have been removed.
   return Type::Any();
 }
@@ skipping 304 matching lines @@
 Type* Typer::Visitor::TypeConstant(Handle<Object> value) {
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::NewConstant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8