[Bindings] Emit less code per member in generated dictionary ToV8.

third_party/WebKit/Source/bindings/tests/results/core/V8TestInterfaceEventInit.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.
 
 // This file has been auto-generated by code_generator_v8.py.
 // DO NOT MODIFY!
 
 // This file has been generated from the Jinja2 template in
 // third_party/WebKit/Source/bindings/templates/dictionary_v8.cpp.tmpl
 
@@ skipping 42 matching lines @@
   v8::Local<v8::Object> v8Object = v8::Object::New(isolate);
   if (!toV8TestInterfaceEventInit(*this, v8Object, creationContext, isolate))
     return v8::Undefined(isolate);
   return v8Object;
 }
 
 bool toV8TestInterfaceEventInit(const TestInterfaceEventInit& impl, v8::Local<v8::Object> dictionary, v8::Local<v8::Object> creationContext, v8::Isolate* isolate) {
   if (!toV8EventInit(impl, dictionary, creationContext, isolate))
     return false;
 
+  v8::Local<v8::Value> stringMemberValue;
+  bool stringMemberHasValueOrDefault = false;
   if (impl.hasStringMember()) {
-    if (!v8CallBoolean(dictionary->CreateDataProperty(isolate->GetCurrentContext(), v8AtomicString(isolate, "stringMember"), v8String(isolate, impl.stringMember()))))
-      return false;
+    stringMemberValue = v8String(isolate, impl.stringMember());
+    stringMemberHasValueOrDefault = true;
+  }
+  if (stringMemberHasValueOrDefault &&
+      !v8CallBoolean(dictionary->CreateDataProperty(isolate->GetCurrentContext(), v8AtomicString(isolate, "stringMember"), stringMemberValue))) {
+    return false;
   }
 
   return true;
 }
 
 TestInterfaceEventInit NativeValueTraits<TestInterfaceEventInit>::nativeValue(v8::Isolate* isolate, v8::Local<v8::Value> value, ExceptionState& exceptionState) {
   TestInterfaceEventInit impl;
   V8TestInterfaceEventInit::toImpl(isolate, value, impl, exceptionState);
   return impl;
 }
 
 }  // namespace blink