Enable CALayerTreeOptimization by default on Mac

Bug: 1294936
Change-Id: Ib48b5320cf3e6348c7ec93540710db2fca7c92b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3840403
Auto-Submit: Maggie Chen <magchen@chromium.org>
Reviewed-by: ccameron chromium <ccameron@chromium.org>
Commit-Queue: ccameron chromium <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1036968}

ui/accelerated_widget_mac/ca_renderer_layer_tree.mm

@@ -38,7 +38,7 @@
 constexpr int kOutputLevel = 4;
 
 base::Feature kCALayerTreeOptimization{"CALayerTreeOptimization",
-                                       base::FEATURE_DISABLED_BY_DEFAULT};
+                                       base::FEATURE_ENABLED_BY_DEFAULT};
 
 void RecordIOSurfaceHistograms(
     int changed_io_surfaces_during_commit,