[Multidevice] Enable improved multi-device drop-down list sorting

By default, sort the multi-device setup drop-down list by the potential
host phones' last activity time. These values are returned from the
CryptAuth server for phones that have already adopted DeviceSync v2.

Note: Some old phones that are not using DeviceSync v2 will not have
this information. Those phones will be displayed after the phones with a
last activity time, and they will be sorted in the same way as before
this flag was enabled.

Bug: 923594
Change-Id: Ib915d1814a2932bf06cd32d9dfdb3be335a520ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2583216
Commit-Queue: Josh Nohle <nohle@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Auto-Submit: Josh Nohle <nohle@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835537}

chromeos/constants/chromeos_features.cc

@@ -209,7 +209,7 @@ const base::Feature kCrostiniEnableDlc{"CrostiniEnableDlc",
 
 // Enables or disables using Cryptauth's GetDevicesActivityStatus API.
 const base::Feature kCryptAuthV2DeviceActivityStatus{
-    "CryptAuthV2DeviceActivityStatus", base::FEATURE_DISABLED_BY_DEFAULT};
+    "CryptAuthV2DeviceActivityStatus", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables or disables use of the connectivity status from Cryptauth's
 // GetDevicesActivityStatus API to sort devices.