Enable app scaling flag

Enable app scaling feature by default. It should be landed after
approval from UX.

Bug: 1097503
Change-Id: I35dd5a7d0fc60a1fbe98cee76d5851ec942c99ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2248168Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781188}

ash/public/cpp/ash_features.cc

@@ -122,7 +122,7 @@ const base::Feature kWebUITabStripTabDragIntegration{
     "WebUITabStripTabDragIntegration", base::FEATURE_DISABLED_BY_DEFAULT};
 
 const base::Feature kShelfAppScaling{"ShelfAppScaling",
-                                     base::FEATURE_DISABLED_BY_DEFAULT};
+                                     base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kNotificationsInContextMenu{
     "NotificationsInContextMenu", base::FEATURE_DISABLED_BY_DEFAULT};