Add ScreenAI feature and flag.

Adds feature and flag to control under development Screen AI module.
Screen AI will use a local machine intelligence library to extract
metadata from snapshots and add metadata for accessibility tools.
See more in http://go/chrome-screen-ai

Bug: 1278249
Change-Id: Ia006206cc7048d25f7398df013e2d6dc8057d863
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3427027
Reviewed-by: Jochen Eisinger <[email protected]>
Commit-Queue: Ramin Halavati <[email protected]>
Cr-Commit-Position: refs/heads/main@{#965601}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 61b9207..3966822 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -3795,6 +3795,11 @@
     "Click on the Bookmark icon or right click on a tab to add tabs to a "
     "reading list.";
 
+const char kScreenAIName[] = "Screen AI";
+const char kScreenAIDescription[] =
+    "Enables Screen AI local machine intelligence library to use the screen "
+    "snapshots to add metadata for accessibility tools.";
+
 const char kSCTAuditingName[] = "SCT auditing";
 const char kSCTAuditingDescription[] =
     "Enables SCT auditing for users who have opted in to Safe Browsing "