Convert --enable-md-history to a feature flag.

chrome/common/chrome_features.cc

 // 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.
 
 #include "chrome/common/chrome_features.h"
 
 namespace features {
 
 // All features in alphabetical order.
 
 #if defined(OS_WIN) || defined(OS_MACOSX)
 // Enables automatic tab discarding, when the system is in low memory state.
 const base::Feature kAutomaticTabDiscarding{"AutomaticTabDiscarding",
                                             base::FEATURE_DISABLED_BY_DEFAULT};
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 
 #if defined(GOOGLE_CHROME_BUILD) && defined(OS_LINUX) && !defined(OS_CHROMEOS)
 // Enables showing the "This computer will no longer receive Google Chrome
 // updates" infobar instead of the "will soon stop receiving" infobar on
 // deprecated systems.
 const base::Feature kLinuxObsoleteSystemIsEndOfTheLine{
     "LinuxObsoleteSystemIsEndOfTheLine", base::FEATURE_DISABLED_BY_DEFAULT};
 #endif
 
+// Enables or disables the Material Design version of chrome://history.
+const base::Feature kMaterialDesignHistoryFeature {
+  "MaterialDesignHistory", base::FEATURE_DISABLED_BY_DEFAULT
+};
+
 #if defined(OS_CHROMEOS)
 // Runtime flag that indicates whether this leak detector should be enabled in
 // the current instance of Chrome.
 const base::Feature kRuntimeMemoryLeakDetector{
     "RuntimeMemoryLeakDetector", base::FEATURE_DISABLED_BY_DEFAULT};
 #endif  // defined(OS_CHROMEOS)
 
 // A new user experience for transitioning into fullscreen and mouse pointer
 // lock states. The name is a misnomer (for historical reasons); affects both
 // Views and Android builds.
 const base::Feature kSimplifiedFullscreenUI{
     "ViewsSimplifiedFullscreenUI",
 #if defined(USE_AURA)
     // Windows, Linux, Chrome OS.
     base::FEATURE_ENABLED_BY_DEFAULT,
 #else
     // Mac, Android.
     base::FEATURE_DISABLED_BY_DEFAULT,
 #endif
 };
 
 }  // namespace features