[Sharesheet] Add flag for Content Previews.

This CL adds a feature flag for enabling the content
previews feature on Chrome OS devices.

Bug: 1156343
Change-Id: Idb4b5c4d7d77b7532e7c585759067893a14912eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2576987
Commit-Queue: Angela Gyi <[email protected]>
Reviewed-by: Melissa Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#835871}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index d1e3216..cf17a85 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -4558,6 +4558,10 @@
     "Enables a separate group of settings (speed, button swap, and "
     "acceleration) for pointing sticks (such as TrackPoints).";
 
+const char kSharesheetContentPreviewsName[] = "Sharesheet Content Previews";
+const char kSharesheetContentPreviewsDescription[] =
+    "Chrome OS content previews for sharesheet.";
+
 const char kSharesheetName[] = "Sharesheet";
 const char kSharesheetDescription[] = "Chrome OS sharesheet.";