Remove some more WTF usage

sky/engine/tonic/dart_state.cc

 // Copyright 2015 The Chromium 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 "sky/engine/tonic/dart_state.h"
 
 #include "sky/engine/tonic/dart_class_library.h"
 #include "sky/engine/tonic/dart_converter.h"
 #include "sky/engine/tonic/dart_exception_factory.h"
 #include "sky/engine/tonic/dart_library_loader.h"
 #include "sky/engine/tonic/dart_string_cache.h"
 #include "sky/engine/tonic/dart_timer_heap.h"
-#include "sky/engine/wtf/PassOwnPtr.h"
 
 namespace blink {
 
 DartState::Scope::Scope(DartState* dart_state) : scope_(dart_state->isolate()) {
 }
 
 DartState::Scope::~Scope() {
 }
 
 DartState::DartState()
@@ skipping 32 matching lines @@
 
 DartState* DartState::Current() {
   return static_cast<DartState*>(Dart_CurrentIsolateData());
 }
 
 base::WeakPtr<DartState> DartState::GetWeakPtr() {
   return weak_factory_.GetWeakPtr();
 }
 
 }  // namespace blink