[Nearby] Add background scanning feature flag.

This CL adds a feature flag for Nearby Share background scanning.

This will initially be used to gate the feature prototype.

Bug: 1223888
Change-Id: Id6714365f3c0abef333e3325efae934dcff2f240
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2986987
Commit-Queue: Michael Hansen <[email protected]>
Reviewed-by: Josh Nohle <[email protected]>
Cr-Commit-Position: refs/heads/master@{#896127}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index a883693..4fd0cc5 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -4812,6 +4812,13 @@
 const char kNearbySharingDescription[] =
     "Enables Nearby Sharing for sharing content between devices.";
 
+const char kNearbySharingBackgroundScanningName[] =
+    "Nearby Sharing Background Scanning";
+const char kNearbySharingBackgroundScanningDescription[] =
+    "Enables background scanning for Nearby Share, allowing devices to "
+    "persistently scan and present a notification when a nearby device is "
+    "attempting to share.";
+
 const char kNearbySharingDeviceContactsName[] =
     "Nearby Sharing Device Contacts";
 const char kNearbySharingDeviceContactsDescription[] =