Introduce chrome://flags/#network-prediction-options-for-service-worker

content/public/browser/service_worker_context.h

 // Copyright 2014 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_SERVICE_WORKER_CONTEXT_H_
 #define CONTENT_PUBLIC_BROWSER_SERVICE_WORKER_CONTEXT_H_
 
 #include <set>
 #include <string>
 
 #include "base/callback_forward.h"
 #include "content/public/browser/service_worker_usage_info.h"
 #include "url/gurl.h"
 
 namespace content {
 
+class RenderProcessHost;
+
 enum class ServiceWorkerCapability {
   NO_SERVICE_WORKER,
   SERVICE_WORKER_NO_FETCH_HANDLER,
   SERVICE_WORKER_WITH_FETCH_HANDLER,
 };
 
 // Represents the per-StoragePartition ServiceWorker data.
 class ServiceWorkerContext {
  public:
   // https://rawgithub.com/slightlyoff/ServiceWorker/master/spec/service_worker/index.html#url-scope:
@@ skipping 105 matching lines @@
   virtual void StopAllServiceWorkersForOrigin(const GURL& origin) = 0;
 
   // Stops all running service workers and unregisters all service worker
   // registrations. This method is used in LayoutTests to make sure that the
   // existing service worker will not affect the succeeding tests.
   //
   // This function can be called from any thread, but the callback will always
   // be called on the UI thread.
   virtual void ClearAllServiceWorkersForTest(const base::Closure& callback) = 0;
 
+  // Starts a Service Worker for |document_url| for a navigation preconnect in
+  // the specified render process |host|. Must be called from the UI thread. The

[falken, 2017/06/01 06:54:17]

The "for... for... in..." is ambiguous: is the document in host, or preconnect
in host?

This function itself also doesn't really have to do NavigationPreconnect. It
just starts the worker and the caller happens to be the predictor, and it's used
even if preconnect won't happen. I wonder if just StartServiceWorker is a better
name?

I'd suggest:

"Starts the service worker whose scope matches |document_url|. The service
worker is started in |host|. This can be used to warm up a service worker for a
navigation."

[horo, 2017/06/01 11:15:07]

I changed it to "StartServiceWorkerForNavigation".
I think we should keep "Navigation" for the method name, because UMAs of
EventType::NAVIGATION will be recorded if this method is called.

[falken, 2017/06/01 23:24:14]

Sorry I totally overlooked the EventType. I think PRECONNECT was a better name
than NAVIGATION for the event type.

I'm concerned we're creating in this separate path for starting a service worker
for navigation different than the normal navigation path (starting a service
worker via URLRequestJob), just to start before the predictor. If we do create
this separate path the name PRECONNECT feels better to make it explicit that
it's a separate path.

It's worth noting that this CL will also affect our metrics about navigations
and timing like:
ServiceWorker.ActivatedWorkerPreparationForMainFrame.

+  // |callback| will always be called on the UI thread. This method can fail if:
+  //  * No Service Worker was registered for |document_url|.
+  //  * The specified render process is not suitable for loading |document_url|.
+  virtual void StartServiceWorkerForNavigationPreconnect(
+      const GURL& document_url,
+      RenderProcessHost* host,
+      const ResultCallback& callback) = 0;
+
  protected:
   ServiceWorkerContext() {}
   virtual ~ServiceWorkerContext() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_SERVICE_WORKER_CONTEXT_H_