[builtins] Migrate String.fromCharCode to TurboFan code stub.

src/runtime/runtime-internal.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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/ast/prettyprinter.h"
 #include "src/bootstrapper.h"
 #include "src/conversions.h"
@@ skipping 307 matching lines @@
   CONVERT_SMI_ARG_CHECKED(size, 0);
   CONVERT_SMI_ARG_CHECKED(flags, 1);
   RUNTIME_ASSERT(IsAligned(size, kPointerSize));
   RUNTIME_ASSERT(size > 0);
   RUNTIME_ASSERT(size <= Page::kMaxRegularHeapObjectSize);
   bool double_align = AllocateDoubleAlignFlag::decode(flags);
   AllocationSpace space = AllocateTargetSpace::decode(flags);
   return *isolate->factory()->NewFillerObject(size, double_align, space);
 }
 
+RUNTIME_FUNCTION(Runtime_AllocateSeqOneByteString) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_SMI_ARG_CHECKED(length, 0);
+  Handle<SeqOneByteString> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result, isolate->factory()->NewRawOneByteString(length));
+  return *result;
+}
+
+RUNTIME_FUNCTION(Runtime_AllocateSeqTwoByteString) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_SMI_ARG_CHECKED(length, 0);
+  Handle<SeqTwoByteString> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result, isolate->factory()->NewRawTwoByteString(length));
+  return *result;
+}
 
 // Collect the raw data for a stack trace.  Returns an array of 4
 // element segments each containing a receiver, function, code and
 // native code offset.
 RUNTIME_FUNCTION(Runtime_CollectStackTrace) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSReceiver, error_object, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, caller, 1);
 
@@ skipping 262 matching lines @@
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   bool is_wasm_object = object->IsJSObject() &&
                         wasm::IsWasmObject(Handle<JSObject>::cast(object));
   return *isolate->factory()->ToBoolean(is_wasm_object);
 }
 
 }  // namespace internal
 }  // namespace v8