Don't wrap roots in Handle just to dereference immediately.

src/builtins/builtins-string.cc

 // 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.
 
 #include "src/builtins/builtins.h"
 #include "src/builtins/builtins-utils.h"
 
 #include "src/code-factory.h"
 #include "src/regexp/regexp-utils.h"
 
@@ skipping 802 matching lines @@
     end = str->length();
   } else {
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, position,
                                        Object::ToInteger(isolate, position));
     double index = std::max(position->Number(), 0.0);
     index = std::min(index, static_cast<double>(str->length()));
     end = static_cast<uint32_t>(index);
   }
 
   int start = end - search_string->length();
-  if (start < 0) return *isolate->factory()->false_value();
+  if (start < 0) return isolate->heap()->false_value();
 
   FlatStringReader str_reader(isolate, String::Flatten(str));
   FlatStringReader search_reader(isolate, String::Flatten(search_string));
 
   for (int i = 0; i < search_string->length(); i++) {
     if (str_reader.Get(start + i) != search_reader.Get(i)) {
-      return *isolate->factory()->false_value();
+      return isolate->heap()->false_value();
     }
   }
-  return *isolate->factory()->true_value();
+  return isolate->heap()->true_value();
 }
 
 // ES6 section 21.1.3.7
 // String.prototype.includes ( searchString [ , position ] )
 BUILTIN(StringPrototypeIncludes) {
   HandleScope handle_scope(isolate);
   TO_THIS_STRING(str, "String.prototype.includes");
 
   // Check if the search string is a regExp and fail if it is.
   Handle<Object> search = args.atOrUndefined(isolate, 1);
@@ skipping 388 matching lines @@
     start = 0;
   } else {
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, position,
                                        Object::ToInteger(isolate, position));
     double index = std::max(position->Number(), 0.0);
     index = std::min(index, static_cast<double>(str->length()));
     start = static_cast<uint32_t>(index);
   }
 
   if (start + search_string->length() > str->length()) {
-    return *isolate->factory()->false_value();
+    return isolate->heap()->false_value();
   }
 
   FlatStringReader str_reader(isolate, String::Flatten(str));
   FlatStringReader search_reader(isolate, String::Flatten(search_string));
 
   for (int i = 0; i < search_string->length(); i++) {
     if (str_reader.Get(start + i) != search_reader.Get(i)) {
-      return *isolate->factory()->false_value();
+      return isolate->heap()->false_value();
     }
   }
-  return *isolate->factory()->true_value();
+  return isolate->heap()->true_value();
 }
 
 // ES6 section 21.1.3.25 String.prototype.toString ()
 void Builtins::Generate_StringPrototypeToString(CodeStubAssembler* assembler) {
   typedef compiler::Node Node;
 
   Node* receiver = assembler->Parameter(0);
   Node* context = assembler->Parameter(3);
 
   Node* result = assembler->ToThisValue(
@@ skipping 227 matching lines @@
         Runtime::kThrowIncompatibleMethodReceiver, context,
         assembler->HeapConstant(assembler->factory()->NewStringFromAsciiChecked(
             "String Iterator.prototype.next", TENURED)),
         iterator);
     assembler->Return(result);  // Never reached.
   }
 }
 
 }  // namespace internal
 }  // namespace v8