Enable ServiceWorkerNavigationPreload by default for Origin-Trial.

content/public/common/content_features.cc

 // Copyright 2015 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.
 
 #include "build/build_config.h"
 #include "content/public/common/content_features.h"
 
 namespace features {
 
 // All features in alphabetical order.
@@ skipping 171 matching lines @@
 
 // Throttle Blink's rendering pipeline based on frame visibility.
 const base::Feature kRenderingPipelineThrottling{
     "RenderingPipelineThrottling", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Scrolls to compensate for layout movements (bit.ly/scroll-anchoring).
 const base::Feature kScrollAnchoring{"ScrollAnchoring",
                                      base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Navigation preload feature of service workers.
-// TODO(horo): Revise link when this lands in the spec:
-// https://github.com/w3c/ServiceWorker/pull/983/files
+// We enable this base::Feature by default for Origin-Trial. But in
+// runtime_features.cc, we enable the blink::WebRuntimeFeatures only when it is
+// enabled by "--enable-features" command line flag. See the comments in
+// runtime_features.cc and service_worker_version.h for the details.

[kinuko, 2017/01/16 05:07:10]

nit: avoid using 'we' in general, e.g. 'Enables this base::Feature by default
for Origin-Trial, but enables the corresponding blink::WebRuntimeFeatures only
when '--enable-features' command line flag is given.  See the...'

[horo, 2017/01/16 05:30:36]

Done.

 const base::Feature kServiceWorkerNavigationPreload{
-    "ServiceWorkerNavigationPreload", base::FEATURE_DISABLED_BY_DEFAULT};
+    "ServiceWorkerNavigationPreload", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // http://tc39.github.io/ecmascript_sharedmem/shmem.html
 const base::Feature kSharedArrayBuffer{"SharedArrayBuffer",
                                        base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Speculatively launches Service Workers on mouse/touch events.
 const base::Feature kSpeculativeLaunchServiceWorker{
     "SpeculativeLaunchServiceWorker", base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enables implementation of the Cache-Control: stale-while-revalidate directive
@@ skipping 77 matching lines @@
 #endif  // !defined(OS_ANDROID)
 
 #if defined(OS_WIN)
 // Emergency "off switch" for new Windows sandbox security mitigation,
 // sandbox::MITIGATION_EXTENSION_POINT_DISABLE.
 const base::Feature kWinSboxDisableExtensionPoints{
     "WinSboxDisableExtensionPoint", base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
 }  // namespace features