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

chrome/browser/flag_descriptions.cc

 // Copyright 2017 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 "chrome/browser/flag_descriptions.h"
 
 namespace flag_descriptions {
 
 const char kBrowserSideNavigationName[] = "Enable browser side navigation";
 
@@ skipping 1042 matching lines @@
 
 const char kEnableNavigationTracingName[] = "Enable navigation tracing";
 
 const char kEnableNavigationTracingDescription[] =
     "This is to be used in conjunction with the trace-upload-url flag. "
     "WARNING: When enabled, Chrome will record performance data for every "
     "navigation and upload it to the URL specified by the trace-upload-url "
     "flag. The trace may include personally identifiable information (PII) "
     "such as the titles and URLs of websites you visit.";
 
+const char kEnableNetworkServiceName[] = "Enable network service";
+
+const char kEnableNetworkServiceDescription[] =
+    "Enables the network service, which makes network requests through a "
+    "separate service. Note: most features don't work with this yet.";
+
 const char kEnablePictureInPictureName[] = "Enable picture in picture.";
 
 const char kEnablePictureInPictureDescription[] =
     "Enable the picture in picture feature for videos.";
 
 const char kTraceUploadUrlName[] = "Trace label for navigation tracing";
 
 const char kTraceUploadUrlDescription[] =
     "This is to be used in conjunction with the enable-navigation-tracing "
     "flag. Please select the label that best describes the recorded traces. "
@@ skipping 2208 matching lines @@
     "in non-sticky mode (do not change work area in non-sticky mode).";
 
 const char kUiDevToolsName[] = "Enable native UI inspection";
 const char kUiDevToolsDescription[] =
     "Enables inspection of native UI elements. For local inspection use "
     "chrome://inspect#other";
 
 #endif  // defined(OS_CHROMEOS)
 
 }  // namespace flag_descriptions