Remove the BackspaceGoesBack flag.

chrome/common/chrome_features.h

 // Copyright 2016 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 chrome
 // module.
 
 #ifndef CHROME_COMMON_CHROME_FEATURES_H_
 #define CHROME_COMMON_CHROME_FEATURES_H_
 
@@ skipping 28 matching lines @@
 #endif
 
 #if defined(OS_WIN) || defined(OS_MACOSX)
 extern const base::Feature kAutomaticTabDiscarding;
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 
 #if defined(OS_WIN) || defined(OS_LINUX)
 extern const base::Feature kBackgroundModeAllowRestart;
 #endif  // defined(OS_WIN) || defined(OS_LINUX)
 
-extern const base::Feature kBackspaceGoesBackFeature;
-
 extern const base::Feature kBlockPromptsIfDismissedOften;
 extern const base::Feature kBlockPromptsIfIgnoredOften;
 
 #if defined(OS_MACOSX)
 extern const base::Feature kBookmarkApps;
 #endif
 
 extern const base::Feature kBrowserHangFixesExperiment;
 
 #if defined(OS_MACOSX)
@@ skipping 130 matching lines @@
 #endif  // defined(OS_CHROMEOS)
 
 bool PrefServiceEnabled();
 
 // 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  // CHROME_COMMON_CHROME_FEATURES_H_