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

src/builtins/builtins-utils.h

 // Copyright 2016 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_BUILTINS_BUILTINS_UTILS_H_
 #define V8_BUILTINS_BUILTINS_UTILS_H_
 
 #include "src/arguments.h"
 #include "src/base/logging.h"
 #include "src/builtins/builtins.h"
 #include "src/code-stub-assembler.h"
 
 namespace v8 {
 namespace internal {
 
 // Arguments object passed to C++ builtins.
 class BuiltinArguments : public Arguments {
  public:
   BuiltinArguments(int length, Object** arguments)
       : Arguments(length, arguments) {
     // Check we have at least the receiver.
     DCHECK_LE(1, this->length());
   }
 
   Object*& operator[](int index) {
     DCHECK_LT(index, length());
     return Arguments::operator[](index);
   }
 
-  template <class S>
+  template <class S = Object>
   Handle<S> at(int index) {
     DCHECK_LT(index, length());
     return Arguments::at<S>(index);
   }
 
   Handle<Object> atOrUndefined(Isolate* isolate, int index) {
     if (index >= length()) {
       return isolate->factory()->undefined_value();
     }
     return at<Object>(index);
@@ skipping 109 matching lines @@
                      isolate->factory()->NewStringFromAsciiChecked(method))); \
   }                                                                           \
   Handle<String> name;                                                        \
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(                                         \
       isolate, name, Object::ToString(isolate, args.receiver()))
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_BUILTINS_BUILTINS_UTILS_H_