PlzNavigate: use a SiteInstance to intialize the ServiceWorkerNavigationHandle

content/browser/frame_host/navigation_request.h

Index: content/browser/frame_host/navigation_request.h
diff --git a/content/browser/frame_host/navigation_request.h b/content/browser/frame_host/navigation_request.h
index 0bd1312c565a15da1cb3d9a9738100eab9e26e2a..ccf9152d495ceaa7c99a9203a104a4a450899381 100644
--- a/content/browser/frame_host/navigation_request.h
+++ b/content/browser/frame_host/navigation_request.h
@@ -162,6 +162,9 @@ class CONTENT_EXPORT NavigationRequest : public NavigationURLLoaderDelegate {
   void OnStartChecksComplete(NavigationThrottle::ThrottleCheckResult result);
   void OnRedirectChecksComplete(NavigationThrottle::ThrottleCheckResult result);
 
+  // Called when the navigation is about to be sent to the IO thread.
+  void InitializeServiceWorkerHandleIfNeeded();
+
   FrameTreeNode* frame_tree_node_;
 
   // Initialized on creation of the NavigationRequest. Sent to the renderer when