Hardcode extensions::util::IsNewBookmarkAppsEnabled() to true, except on Mac.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 49f6b5d95519744d9557a60cc5a2c3a0c90b560c..b649390288c78198238cc818e5f83f9f0698948d 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -232,9 +232,6 @@ const char kDisableHttp2[] = "disable-http2";
 const char kDisableMinimizeOnSecondLauncherItemClick[] =
     "disable-minimize-on-second-launcher-item-click";
 
-// Disables the new bookmark app system.
-const char kDisableNewBookmarkApps[]        = "disable-new-bookmark-apps";
-
 // Disable auto-reload of error pages if offline.
 const char kDisableOfflineAutoReload[]      = "disable-offline-auto-reload";
 
@@ -368,9 +365,6 @@ const char kEnableNavigationTracing[] = "enable-navigation-tracing";
 // Enables the network-related benchmarking extensions.
 const char kEnableNetBenchmarking[]         = "enable-net-benchmarking";
 
-// Enables the new bookmark app system.
-const char kEnableNewBookmarkApps[]         = "enable-new-bookmark-apps";
-
 // Enable auto-reload of error pages if offline.
 const char kEnableOfflineAutoReload[]       = "enable-offline-auto-reload";