Add about:flags control for toggling sync server sandbox

chrome/browser/about_flags.cc

 // Copyright (c) 2012 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/about_flags.h"
 
 #include <iterator>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 2172 matching lines @@
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kAllowInsecureLocalhost)
   },
   {
     "bypass-app-banner-engagement-checks",
     IDS_FLAGS_BYPASS_APP_BANNER_ENGAGEMENT_CHECKS_NAME,
     IDS_FLAGS_BYPASS_APP_BANNER_ENGAGEMENT_CHECKS_DESCRIPTION,
     kOsAndroid,
     SINGLE_VALUE_TYPE(switches::kBypassAppBannerEngagementChecks)
   },
+  {
+    "use-sync-sandbox",
+    IDS_FLAGS_SYNC_SANDBOX_NAME,
+    IDS_FLAGS_SYNC_SANDBOX_DESCRIPTION,
+    kOsAll,
+    SINGLE_VALUE_TYPE_AND_VALUE(
+        switches::kSyncServiceUrl,
+        "https://chrome-sync.sandbox.google.com/chrome-sync/alpha")
+  },
 
   // NOTE: Adding new command-line switches requires adding corresponding
   // entries to enum "LoginCustomFlags" in histograms.xml. See note in
   // histograms.xml and don't forget to run AboutFlagsHistogramTest unit test.
 };
 
 const Experiment* experiments = kExperiments;
 size_t num_experiments = arraysize(kExperiments);
 
 // Stores and encapsulates the little state that about:flags has.
@@ skipping 583 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags