Clean up DownloadAttribution Finch experiments

components/safe_browsing/csd.proto

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // This proto file includes:
 // (1) Client side phishing and malware detection request and response
 //   protocol buffers.  Those protocol messages should be kept in sync
 //   with the server implementation.
 //
 // (2) Safe Browsing reporting protocol buffers.
@@ skipping 471 matching lines @@
   // PPAPI_SAVE_REQUEST type messages may have more than one suggested filetype.
   // Each element in this collection indicates an alternate extension including
   // the leading extension separator.
   repeated string alternate_extensions = 35;
 
   // URLs transitions from landing referrer to download in reverse chronological
   // order, i.e. download url comes first in this list, and landing referrer
   // comes last.
   repeated ReferrerChainEntry referrer_chain = 36;
 
-  // Whether DownloadAttribution Finch experiment is enabled for this ping.
-  optional bool download_attribution_finch_enabled = 39;
+  // Deprecated.
+  optional bool DEPRECATED_download_attribution_finch_enabled = 39
+      [deprecated = true];
 }
 
 message ReferrerChainEntry {
   enum URLType {
     // URL of safe browsing events that are at the end of the referrer chain.
     // e.g. URL of a download, URL of a low reputation login page, etc.
     EVENT_URL = 1;  // e.g.
 
     // Landing page is the page user directly interacts with to trigger the
     // above event, e.g. the page where user clicks a download button.
@@ skipping 519 matching lines @@
 // There is no response (an empty body) to this request.
 message NotificationImageReportRequest {
   optional string notification_origin = 1;  // Src-origin of the notification.
   optional ImageData image = 2;             // The bitmap of the image.
 
   // Note that the image URL is deliberately omitted as it would be untrusted,
   // since the notification image fetch may be intercepted by a Service Worker
   // (even if the image URL is cross-origin). Otherwise a website could mislead
   // Safe Browsing into associating phishing image bitmaps with safe image URLs.
 }