Add once field to devtools so it can be queried by lighthouse.

third_party/WebKit/Source/core/inspector/ThreadDebugger.cpp

 // Copyright 2016 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 "core/inspector/ThreadDebugger.h"
 
 #include "bindings/core/v8/SourceLocation.h"
 #include "bindings/core/v8/V8Binding.h"
 #include "bindings/core/v8/V8DOMException.h"
 #include "bindings/core/v8/V8DOMTokenList.h"
@@ skipping 396 matching lines @@
                          listeners);
     }
 
     v8::Local<v8::Object> listenerObject = v8::Object::New(isolate);
     createDataProperty(context, listenerObject, v8String(isolate, "listener"),
                        info.handler);
     createDataProperty(context, listenerObject, v8String(isolate, "useCapture"),
                        v8::Boolean::New(isolate, info.useCapture));
     createDataProperty(context, listenerObject, v8String(isolate, "passive"),
                        v8::Boolean::New(isolate, info.passive));
+    createDataProperty(context, listenerObject, v8String(isolate, "once"),
+                       v8::Boolean::New(isolate, info.once));
     createDataProperty(context, listenerObject, v8String(isolate, "type"),
                        v8String(isolate, currentEventType));
     v8::Local<v8::Function> removeFunction;
     if (info.removeFunction.ToLocal(&removeFunction))
       createDataProperty(context, listenerObject, v8String(isolate, "remove"),
                          removeFunction);
     createDataPropertyInArray(context, listeners, outputIndex++,
                               listenerObject);
   }
   info.GetReturnValue().Set(result);
@@ skipping 52 matching lines @@
 void ThreadDebugger::onTimer(TimerBase* timer) {
   for (size_t index = 0; index < m_timers.size(); ++index) {
     if (m_timers[index].get() == timer) {
       m_timerCallbacks[index](m_timerData[index]);
       return;
     }
   }
 }
 
 }  // namespace blink