Add a feature flag for network service and about:flags entry for it.

content/public/common/content_features.h

 // 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.
 
 // This file defines all the public base::FeatureList features for the content
 // module.
 
 #ifndef CONTENT_PUBLIC_COMMON_CONTENT_FEATURES_H_
 #define CONTENT_PUBLIC_COMMON_CONTENT_FEATURES_H_
 
@@ skipping 28 matching lines @@
     kFramebustingNeedsSameOriginOrUserGesture;
 CONTENT_EXPORT extern const base::Feature kGamepadExtensions;
 CONTENT_EXPORT extern const base::Feature kGuestViewCrossProcessFrames;
 CONTENT_EXPORT extern const base::Feature kHeapCompaction;
 CONTENT_EXPORT extern const base::Feature kIdleTimeSpellChecking;
 CONTENT_EXPORT extern const base::Feature kLazyParseCSS;
 CONTENT_EXPORT extern const base::Feature kLoadingWithMojo;
 CONTENT_EXPORT extern const base::Feature kMediaDocumentDownloadButton;
 CONTENT_EXPORT extern const base::Feature kMediaStreamOldAudioConstraints;
 CONTENT_EXPORT extern const base::Feature kMemoryCoordinator;
+CONTENT_EXPORT extern const base::Feature kNetworkService;
 CONTENT_EXPORT extern const base::Feature kNotificationContentImage;
 CONTENT_EXPORT extern const base::Feature kMainThreadBusyScrollIntervention;
 CONTENT_EXPORT extern const base::Feature kMojoBlobs;
 CONTENT_EXPORT extern const base::Feature kMojoInputMessages;
 CONTENT_EXPORT extern const base::Feature kModuleScripts;
 CONTENT_EXPORT extern const base::Feature kOffMainThreadFetch;
 CONTENT_EXPORT extern const base::Feature kOriginTrials;
 CONTENT_EXPORT extern const base::Feature kParallelDownloading;
 CONTENT_EXPORT extern const base::Feature kPassiveDocumentEventListeners;
 CONTENT_EXPORT extern const base::Feature kPassiveEventListenersDueToFling;
@@ skipping 49 matching lines @@
 #if defined(OS_MACOSX)
 CONTENT_EXPORT extern const base::Feature kMacV2Sandbox;
 #endif  // defined(OS_MACOSX)
 
 // DON'T ADD RANDOM STUFF HERE. Put it in the main section above in
 // alphabetical order, or in one of the ifdefs (also in order in each section).
 
 }  // namespace features
 
 #endif  // CONTENT_PUBLIC_COMMON_CONTENT_FEATURES_H_