Implement BackgroundFetchManager.fetch() and struct traits

third_party/WebKit/Source/modules/background_fetch/BackgroundFetchRegistration.cpp

Index: third_party/WebKit/Source/modules/background_fetch/BackgroundFetchRegistration.cpp
diff --git a/third_party/WebKit/Source/modules/background_fetch/BackgroundFetchRegistration.cpp b/third_party/WebKit/Source/modules/background_fetch/BackgroundFetchRegistration.cpp
index b5ed2d0963c5fe4398dcb62928ec19d45d3caae8..0cacfa61863c80bed90dd379f67cd3095381ffc0 100644
--- a/third_party/WebKit/Source/modules/background_fetch/BackgroundFetchRegistration.cpp
+++ b/third_party/WebKit/Source/modules/background_fetch/BackgroundFetchRegistration.cpp
@@ -11,19 +11,22 @@
 namespace blink {
 
 BackgroundFetchRegistration::BackgroundFetchRegistration(
-    ServiceWorkerRegistration* registration,
     String tag,
     HeapVector<IconDefinition> icons,
     long long totalDownloadSize,
     String title)
-    : m_registration(registration),
-      m_tag(tag),
+    : m_tag(tag),
       m_icons(icons),
       m_totalDownloadSize(totalDownloadSize),
       m_title(title) {}
 
 BackgroundFetchRegistration::~BackgroundFetchRegistration() = default;
 
+void BackgroundFetchRegistration::setServiceWorkerRegistration(
+    ServiceWorkerRegistration* registration) {
+  m_registration = registration;
+}
+
 String BackgroundFetchRegistration::tag() const {
   return m_tag;
 }
@@ -41,6 +44,7 @@ String BackgroundFetchRegistration::title() const {
 }
 
 void BackgroundFetchRegistration::abort() {
+  DCHECK(m_registration);
   BackgroundFetchBridge::from(m_registration)->abort(m_tag);
 }