This CL is a workaround fix for a crash issue; to set "undefined" instead of deleting properties.

third_party/WebKit/Source/bindings/core/v8/ScriptPromisePropertyBase.cpp

 // Copyright 2014 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 "bindings/core/v8/ScriptPromisePropertyBase.h"
 
 #include <memory>
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/V8Binding.h"
@@ skipping 143 matching lines @@
 }
 
 void ScriptPromisePropertyBase::ClearWrappers() {
   CheckThis();
   CheckWrappers();
   v8::HandleScope handle_scope(isolate_);
   for (WeakPersistentSet::iterator i = wrappers_.begin(); i != wrappers_.end();
        ++i) {
     v8::Local<v8::Object> wrapper = (*i)->NewLocal(isolate_);
     if (!wrapper.IsEmpty()) {
-      ResolverSymbol().DeleteProperty(wrapper);
       // TODO(peria): Use deleteProperty() if http://crbug.com/v8/6227 is fixed.
+      ResolverSymbol().Set(wrapper, v8::Undefined(isolate_));
       PromiseSymbol().Set(wrapper, v8::Undefined(isolate_));
     }
   }
   wrappers_.Clear();
 }
 
 void ScriptPromisePropertyBase::CheckThis() {
   RELEASE_ASSERT(this);
 }
 
@@ skipping 32 matching lines @@
   }
   NOTREACHED();
   return V8PrivateProperty::GetSymbol(isolate_, "noResolver");
 }
 
 DEFINE_TRACE(ScriptPromisePropertyBase) {
   ContextClient::Trace(visitor);
 }
 
 }  // namespace blink