[runtime] Port simple String.prototype.indexOf cases to TF Builtin

src/arguments.h

 // Copyright 2012 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.
 
 #ifndef V8_ARGUMENTS_H_
 #define V8_ARGUMENTS_H_
 
 #include "src/allocation.h"
 #include "src/objects-inl.h"
 #include "src/tracing/trace-event.h"
@@ skipping 23 matching lines @@
     DCHECK_GE(length_, 0);
   }
 
   Object*& operator[] (int index) {
     DCHECK_GE(index, 0);
     DCHECK_LT(static_cast<uint32_t>(index), static_cast<uint32_t>(length_));
     return *(reinterpret_cast<Object**>(reinterpret_cast<intptr_t>(arguments_) -
                                         index * kPointerSize));
   }
 
-  template <class S> Handle<S> at(int index) {
+  template <class S = Object>
+  Handle<S> at(int index) {
     Object** value = &((*this)[index]);
     // This cast checks that the object we're accessing does indeed have the
     // expected type.
     S::cast(*value);
     return Handle<S>(reinterpret_cast<S**>(value));
   }
 
   int smi_at(int index) {
     return Smi::cast((*this)[index])->value();
   }
@@ skipping 53 matching lines @@
 #define RUNTIME_FUNCTION(Name) RUNTIME_FUNCTION_RETURNS_TYPE(Object*, Name)
 #define RUNTIME_FUNCTION_RETURN_PAIR(Name) \
     RUNTIME_FUNCTION_RETURNS_TYPE(ObjectPair, Name)
 #define RUNTIME_FUNCTION_RETURN_TRIPLE(Name) \
     RUNTIME_FUNCTION_RETURNS_TYPE(ObjectTriple, Name)
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ARGUMENTS_H_