[builtins] Move StringLastIndexOf to a builtin.

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"
 
 namespace v8 {
@@ skipping 459 matching lines @@
     assembler->Return(assembler->NaNConstant());
     assembler->Bind(&if_positioninbounds);
   }
 
   // Load the character at the {position} from the {receiver}.
   Node* value = assembler->StringCharCodeAt(receiver, position);
   Node* result = assembler->SmiFromWord32(value);
   assembler->Return(result);
 }
 
+// ES6 section 21.1.3.9
+// String.prototype.lastIndexOf ( searchString [ , position ] )
+BUILTIN(StringPrototypeLastIndexOf) {
+  HandleScope handle_scope(isolate);
+  return String::LastIndexOf(isolate, args.receiver(),
+                             args.atOrUndefined(isolate, 1),
+                             args.atOrUndefined(isolate, 2));
+}
+
 // ES6 section 21.1.3.10 String.prototype.localeCompare ( that )
 //
 // This function is implementation specific.  For now, we do not
 // do anything locale specific.
 // If internationalization is enabled, then i18n.js will override this function
 // and provide the proper functionality, so this is just a fallback.
 BUILTIN(StringPrototypeLocaleCompare) {
   HandleScope handle_scope(isolate);
   DCHECK_EQ(2, args.length());
 
@@ skipping 112 matching lines @@
   Node* receiver = assembler->Parameter(0);
   Node* context = assembler->Parameter(3);
 
   Node* result = assembler->ToThisValue(
       context, receiver, PrimitiveType::kString, "String.prototype.valueOf");
   assembler->Return(result);
 }
 
 }  // namespace internal
 }  // namespace v8