Move enable_app_list to a buildflag.

chrome/common/pref_names.h

Index: chrome/common/pref_names.h
diff --git a/chrome/common/pref_names.h b/chrome/common/pref_names.h
index e7f91db7cc312e7fd5ea5e8f796fadd8e414aac0..01369f5449649462a2a4deb4160fa3214469eaca 100644
--- a/chrome/common/pref_names.h
+++ b/chrome/common/pref_names.h
@@ -15,7 +15,7 @@
 namespace prefs {
 
 // Profile prefs. Please add Local State prefs below instead.
-#if defined(OS_CHROMEOS) && defined(ENABLE_APP_LIST)
+#if defined(OS_CHROMEOS) && BUILDFLAG(ENABLE_APP_LIST)
 extern const char kArcApps[];
 extern const char kArcBackupRestoreEnabled[];
 extern const char kArcEnabled[];
@@ -758,7 +758,7 @@ extern const char kRLZBrand[];
 extern const char kRLZDisabled[];
 #endif
 
-#if defined(ENABLE_APP_LIST)
+#if BUILDFLAG(ENABLE_APP_LIST)
 extern const char kAppListProfile[];
 extern const char kLastAppListLaunchPing[];
 extern const char kAppListLaunchCount[];
@@ -773,7 +773,7 @@ extern const char kAppLauncherShortcutVersion[];
 extern const char kShowAppLauncherPromo[];
 extern const char kAppLauncherDriveAppMapping[];
 extern const char kAppLauncherUninstalledDriveApps[];
-#endif  // defined(ENABLE_APP_LIST)
+#endif  // BUILDFLAG(ENABLE_APP_LIST)
 
 #if defined(OS_WIN)
 extern const char kAppLaunchForMetroRestart[];