ParentNode#appendChild(null) shouldn't crash

sky/engine/tonic/dart_state.h

 // 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.
 
 #ifndef SKY_ENGINE_TONIC_DART_STATE_H_
 #define SKY_ENGINE_TONIC_DART_STATE_H_
 
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "base/supports_user_data.h"
 #include "dart/runtime/include/dart_api.h"
 #include "sky/engine/wtf/OwnPtr.h"
 #include "sky/engine/wtf/PassRefPtr.h"
 #include "sky/engine/wtf/RefCounted.h"
 
 namespace blink {
 class DartStringCache;
 class DartClassLibrary;
+class DartExceptionFactory;
 
 // DartState represents the state associated with a given Dart isolate. The
 // lifetime of this object is controlled by the DartVM. If you want to hold a
 // reference to a DartState instance, please hold a base::WeakPtr<DartState>.
 //
 // DartState is analogous to gin::PerIsolateData and JSC::ExecState.
 class DartState : public base::SupportsUserData {
  public:
   class Scope {
    public:
@@ skipping 10 matching lines @@
   base::WeakPtr<DartState> GetWeakPtr();
 
   Dart_Isolate isolate() { return isolate_; }
   void set_isolate(Dart_Isolate isolate) {
     CHECK(!isolate_);
     isolate_ = isolate;
   }
 
   DartClassLibrary& class_library() { return *class_library_; }
   DartStringCache& string_cache() { return *string_cache_; }
+  DartExceptionFactory& exception_factory() { return *exception_factory_; }
 
  private:
   Dart_Isolate isolate_;
   OwnPtr<DartClassLibrary> class_library_;
   OwnPtr<DartStringCache> string_cache_;
+  OwnPtr<DartExceptionFactory> exception_factory_;
 
   base::WeakPtrFactory<DartState> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DartState);
 };
 
 }  // namespace blink
 
 #endif  // SKY_ENGINE_TONIC_DART_STATE_H_