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

chrome/common/chrome_features.cc

Index: chrome/common/chrome_features.cc
diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
index 5b0ceda3f8b4a3876502a7f790237e24162884b1..c31156658603f5f5feecd2fd5f6fca1e3a754653 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -65,6 +65,12 @@ const base::Feature kBackspaceGoesBackFeature {
 const base::Feature kBlockPromptsIfDismissedOften{
     "BlockPromptsIfDismissedOften", base::FEATURE_DISABLED_BY_DEFAULT};
 
+#if defined(OS_MACOSX)
+// Enables the new bookmark app system (e.g. Add To Applications on Mac).
+const base::Feature kBookmarkApps{"BookmarkAppsMac",
+                                  base::FEATURE_DISABLED_BY_DEFAULT};
+#endif
+
 // Fixes for browser hang bugs are deployed in a field trial in order to measure
 // their impact. See crbug.com/478209.
 const base::Feature kBrowserHangFixesExperiment{