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

src/elements.cc

 // 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.
 
 #include "src/elements.h"
 
 #include "src/arguments.h"
 #include "src/conversions.h"
 #include "src/factory.h"
 #include "src/isolate-inl.h"
@@ skipping 3681 matching lines @@
 }
 
 
 MaybeHandle<Object> ArrayConstructInitializeElements(Handle<JSArray> array,
                                                      Arguments* args) {
   if (args->length() == 0) {
     // Optimize the case where there are no parameters passed.
     JSArray::Initialize(array, JSArray::kPreallocatedArrayElements);
     return array;
 
-  } else if (args->length() == 1 && args->at<Object>(0)->IsNumber()) {
+  } else if (args->length() == 1 && args->at(0)->IsNumber()) {
     uint32_t length;
-    if (!args->at<Object>(0)->ToArrayLength(&length)) {
+    if (!args->at(0)->ToArrayLength(&length)) {
       return ThrowArrayLengthRangeError(array->GetIsolate());
     }
 
     // Optimize the case where there is one argument and the argument is a small
     // smi.
     if (length > 0 && length < JSArray::kInitialMaxFastElementArray) {
       ElementsKind elements_kind = array->GetElementsKind();
       JSArray::Initialize(array, length, length);
 
       if (!IsFastHoleyElementsKind(elements_kind)) {
@@ skipping 138 matching lines @@
     insertion_index += len;
   }
 
   DCHECK_EQ(insertion_index, result_len);
   return result_array;
 }
 
 ElementsAccessor** ElementsAccessor::elements_accessors_ = NULL;
 }  // namespace internal
 }  // namespace v8