service worker: Add NavigationPreload runtime flag and skeleton interface

third_party/WebKit/Source/modules/serviceworkers/ServiceWorker.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 31 matching lines @@
     ActiveScriptWrappable,
     DependentLifetime,
 ] interface ServiceWorker : EventTarget {
 
     [PostMessage, RaisesException] void postMessage(SerializedScriptValue message, optional sequence<Transferable> transfer);
 
     readonly attribute USVString scriptURL;
     readonly attribute ServiceWorkerState  state;
 
     attribute EventHandler onstatechange;
+
+    [CallWith=ScriptState,RuntimeEnabled=ServiceWorkerNavigationPreload] Promise<Dictionary> getNavigationPreload();

[horo, 2016/10/03 14:05:16]

ditto

+    [CallWith=ScriptState,RuntimeEnabled=ServiceWorkerNavigationPreload] Promise<void> setNavigationPreload(NavigationPreloadOptions options);
 };
 
 ServiceWorker implements AbstractWorker;