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

Index: third_party/WebKit/Source/bindings/core/v8/ScriptPromisePropertyBase.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/ScriptPromisePropertyBase.cpp b/third_party/WebKit/Source/bindings/core/v8/ScriptPromisePropertyBase.cpp
index f684590795a1d4745a56b24d64e0f5f533514e30..230d6a019d9aca47eed4af978d4ad9da858e08ff 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ScriptPromisePropertyBase.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/ScriptPromisePropertyBase.cpp
@@ -161,8 +161,8 @@ void ScriptPromisePropertyBase::ClearWrappers() {
        ++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_));
     }
   }