[Android] Add enhanced bookmark opt-in flag.

chrome/browser/bookmarks/enhanced_bookmarks_features.h

Index: chrome/browser/bookmarks/enhanced_bookmarks_features.h
diff --git a/chrome/browser/bookmarks/enhanced_bookmarks_features.h b/chrome/browser/bookmarks/enhanced_bookmarks_features.h
index a8ee358b7150aede6febbaf9019414da5134fe42..b85b342163a9bfc20f058d541e6666ef8db14406 100644
--- a/chrome/browser/bookmarks/enhanced_bookmarks_features.h
+++ b/chrome/browser/bookmarks/enhanced_bookmarks_features.h
@@ -10,6 +10,7 @@
 #include "extensions/common/extension.h"
 
 class PrefService;
+class Profile;
 
 // States for bookmark experiment. They are set by Chrome sync into
 // sync_driver::prefs::kEnhancedBookmarksExperimentEnabled user preference and
@@ -30,14 +31,20 @@ enum BookmarksExperimentState {
 bool GetBookmarksExperimentExtensionID(const PrefService* user_prefs,
                                        std::string* extension_id);
 
-// Updates bookmark experiment state based on information from Chrome sync
-// and Finch experiments.
+// Updates bookmark experiment state based on information from Chrome sync,
+// Finch experiments, and command line flag.
 void UpdateBookmarksExperimentState(
     PrefService* user_prefs,
     PrefService* local_state,
     bool user_signed_in,
     BookmarksExperimentState experiment_enabled_from_sync);
 
+// Same as UpdateBookmarksExperimentState, but the last argument with
+// BOOKMARKS_EXPERIMENT_ENABLED_FROM_SYNC_UNKNOWN.
+// Intended for performing initial configuration of bookmarks experiments
+// when the browser is first initialized.
+void InitBookmarksExperimentState(Profile* profile);
+
 // Sets flag to opt-in user into Finch experiment.
 void ForceFinchBookmarkExperimentIfNeeded(
     PrefService* local_state,