Move enable_app_list to a buildflag.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index dd5c76a1a64024895952624e5f6be75174fe8bd8..61bad4bfe79ae70af6ee343cb6d0b9972faa97c3 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -98,7 +98,7 @@
 #include "chrome/browser/ui/browser_dialogs.h"
 #endif  // OS_MACOSX
 
-#if defined(ENABLE_APP_LIST)
+#if BUILDFLAG(ENABLE_APP_LIST)
 #include "ui/app_list/app_list_switches.h"
 #endif  // ENABLE_APP_LIST
 
@@ -1045,7 +1045,7 @@ const FeatureEntry kFeatureEntries[] = {
      IDS_FLAGS_SUPERVISED_USER_MANAGED_BOOKMARKS_FOLDER_NAME,
      IDS_FLAGS_SUPERVISED_USER_MANAGED_BOOKMARKS_FOLDER_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableSupervisedUserManagedBookmarksFolder)},
-#if defined(ENABLE_APP_LIST)
+#if BUILDFLAG(ENABLE_APP_LIST)
     {"enable-sync-app-list", IDS_FLAGS_SYNC_APP_LIST_NAME,
      IDS_FLAGS_SYNC_APP_LIST_DESCRIPTION, kOsDesktop,
      ENABLE_DISABLE_VALUE_TYPE(app_list::switches::kEnableSyncAppList,
@@ -1197,7 +1197,7 @@ const FeatureEntry kFeatureEntries[] = {
     {"enable-google-profile-info", IDS_FLAGS_GOOGLE_PROFILE_INFO_NAME,
      IDS_FLAGS_GOOGLE_PROFILE_INFO_DESCRIPTION, kOsMac | kOsWin | kOsLinux,
      SINGLE_VALUE_TYPE(switches::kGoogleProfileInfo)},
-#if defined(ENABLE_APP_LIST)
+#if BUILDFLAG(ENABLE_APP_LIST)
     {"reset-app-list-install-state",
      IDS_FLAGS_RESET_APP_LIST_INSTALL_STATE_NAME,
      IDS_FLAGS_RESET_APP_LIST_INSTALL_STATE_DESCRIPTION,
@@ -1522,7 +1522,7 @@ const FeatureEntry kFeatureEntries[] = {
 #endif  // ENABLE_MEDIA_ROUTER) && !defined(OS_ANDROID
 // Since Drive Search is not available when app list is disabled, flag guard
 // enable-drive-search-in-chrome-launcher flag.
-#if defined(ENABLE_APP_LIST)
+#if BUILDFLAG(ENABLE_APP_LIST)
     {"enable-drive-search-in-app-launcher",
      IDS_FLAGS_DRIVE_SEARCH_IN_CHROME_LAUNCHER,
      IDS_FLAGS_DRIVE_SEARCH_IN_CHROME_LAUNCHER_DESCRIPTION, kOsCrOS,