Implement BackgroundFetchManager.fetch() and struct traits

third_party/WebKit/Source/modules/background_fetch/BUILD.gn

 # Copyright 2017 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.
 
 import("//third_party/WebKit/Source/modules/modules.gni")
 
 blink_modules_sources("background_fetch") {
   sources = [
     "BackgroundFetchBridge.cpp",
     "BackgroundFetchBridge.h",
     "BackgroundFetchClickEvent.cpp",
     "BackgroundFetchClickEvent.h",
     "BackgroundFetchEvent.cpp",
     "BackgroundFetchEvent.h",
     "BackgroundFetchFailEvent.cpp",
     "BackgroundFetchFailEvent.h",
     "BackgroundFetchFetch.cpp",
     "BackgroundFetchFetch.h",
     "BackgroundFetchManager.cpp",
     "BackgroundFetchManager.h",
     "BackgroundFetchRegistration.cpp",
     "BackgroundFetchRegistration.h",
     "BackgroundFetchSettledFetch.cpp",
     "BackgroundFetchSettledFetch.h",
+    "BackgroundFetchTypeConverters.cpp",
+    "BackgroundFetchTypeConverters.h",
     "BackgroundFetchedEvent.cpp",
     "BackgroundFetchedEvent.h",
     "ServiceWorkerGlobalScopeBackgroundFetch.h",
     "ServiceWorkerRegistrationBackgroundFetch.cpp",
     "ServiceWorkerRegistrationBackgroundFetch.h",
   ]
 }