[Android] Add enhanced bookmark opt-in flag.

chrome/browser/bookmarks/enhanced_bookmarks_features.cc

 // Copyright 2013 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/bookmarks/enhanced_bookmarks_features.h"
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_service.h"
 #include "base/prefs/scoped_user_pref_update.h"
@@ skipping 111 matching lines @@
              BOOKMARKS_EXPERIMENT_ENABLED_USER_OPT_OUT) {
     if (opt_out) {
       bookmarks_experiment_new_state =
           BOOKMARKS_EXPERIMENT_ENABLED_USER_OPT_OUT;
     } else {
       // User opted in again.
       bookmarks_experiment_new_state = BOOKMARKS_EXPERIMENT_ENABLED;
     }
   }
 
+#if defined(OS_ANDROID)
+  bool opt_in = !opt_out
+      && CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kEnhancedBookmarksExperiment) == "1";
+  if (opt_in && bookmarks_experiment_new_state == BOOKMARKS_EXPERIMENT_NONE)
+    bookmarks_experiment_new_state = BOOKMARKS_EXPERIMENT_ENABLED;
+#endif
+
   UMA_HISTOGRAM_ENUMERATION("EnhancedBookmarks.SyncExperimentState",
                             bookmarks_experiment_new_state,
                             BOOKMARKS_EXPERIMENT_ENUM_SIZE);
   user_prefs->SetInteger(
       sync_driver::prefs::kEnhancedBookmarksExperimentEnabled,
       bookmarks_experiment_new_state);
   ForceFinchBookmarkExperimentIfNeeded(flags_storage,
                                        bookmarks_experiment_new_state);
 }
 
@@ skipping 76 matching lines @@
   if (CommandLine::ForCurrentProcess()->
       HasSwitch(switches::kEnableSyncArticles)) {
     return true;
   }
   if (variations::GetVariationParamValue(
           kFieldTrialName, "enable-sync-articles") == "1")
     return true;
 
   return false;
 }