[runtime] Rewrite Function.prototype.toString in C++.

src/runtime/runtime-generator.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/factory.h"
 #include "src/frames-inl.h"
 #include "src/objects-inl.h"
@@ skipping 191 matching lines @@
     RUNTIME_ASSERT(0 <= offset && offset < code->Size());
     Address pc = code->address() + offset;
 
     return Smi::FromInt(code->SourcePosition(pc));
   }
 
   return isolate->heap()->undefined_value();
 }
 
 
-RUNTIME_FUNCTION(Runtime_FunctionIsGenerator) {
-  SealHandleScope shs(isolate);
-  DCHECK(args.length() == 1);
-  CONVERT_ARG_CHECKED(JSFunction, f, 0);
-  return isolate->heap()->ToBoolean(f->shared()->is_generator());
-}
-
-
 RUNTIME_FUNCTION(Runtime_GeneratorNext) {
   UNREACHABLE();  // Optimization disabled in SetUpGenerators().
   return NULL;
 }
 
 
 RUNTIME_FUNCTION(Runtime_GeneratorThrow) {
   UNREACHABLE();  // Optimization disabled in SetUpGenerators().
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8