service worker: Add NavigationPreload runtime flag and skeleton interface

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

Index: third_party/WebKit/Source/modules/serviceworkers/ServiceWorker.h
diff --git a/third_party/WebKit/Source/modules/serviceworkers/ServiceWorker.h b/third_party/WebKit/Source/modules/serviceworkers/ServiceWorker.h
index 2066333d4a62d32fb0733b4cead947f7f8e0b41e..dd1bb3bbf58ffa4e942e45e0ebd02cb0010d07f0 100644
--- a/third_party/WebKit/Source/modules/serviceworkers/ServiceWorker.h
+++ b/third_party/WebKit/Source/modules/serviceworkers/ServiceWorker.h
@@ -43,6 +43,7 @@
 
 namespace blink {
 
+class NavigationPreloadOptions;
 class ScriptPromiseResolver;
 
 class MODULES_EXPORT ServiceWorker final : public AbstractWorker,
@@ -70,6 +71,10 @@ class MODULES_EXPORT ServiceWorker final : public AbstractWorker,
   String state() const;
   DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
 
+  ScriptPromise getNavigationPreload(ScriptState*);
+  ScriptPromise setNavigationPreload(ScriptState*,
+                                     const NavigationPreloadOptions&);
+
   // ScriptWrappable overrides.
   bool hasPendingActivity() const final;