Improve memory usage of safe browsing navigation oberver manager.

chrome/browser/safe_browsing/download_protection_service.cc

 // 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.
 
 #include "chrome/browser/safe_browsing/download_protection_service.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 1340 matching lines @@
       if (alternate_extension.empty())
         continue;
       DCHECK_EQ(base::FilePath::kExtensionSeparator, alternate_extension[0]);
       *(request.add_alternate_extensions()) =
           base::FilePath(alternate_extension).AsUTF8Unsafe();
     }
     if (supported_path_ != default_file_path_) {
       *(request.add_alternate_extensions()) =
           base::FilePath(default_file_path_.FinalExtension()).AsUTF8Unsafe();
     }
-    service_->AddReferrerChainToClientDownloadRequest(
-      requestor_url_,
-      nullptr,
-      &request);
+
+    // TODO(676691): We should add reliable download referrer chain for PPAPI
+    // downloads too.
 
     if (!request.SerializeToString(&client_download_request_data_)) {
       // More of an internal error than anything else. Note that the UNKNOWN
       // verdict gets interpreted as "allowed".
       Finish(RequestOutcome::REQUEST_MALFORMED, UNKNOWN);
       return;
     }
 
     service_->ppapi_download_request_callbacks_.Notify(&request);
     DVLOG(2) << "Sending a PPAPI download request for URL: " << request.url();
@@ skipping 439 matching lines @@
           download_tab_id,
           kDownloadAttributionUserGestureLimit,
           &attribution_chain);
   UMA_HISTOGRAM_COUNTS_100(
       "SafeBrowsing.ReferrerURLChainSize.DownloadAttribution",
       attribution_chain.size());
   UMA_HISTOGRAM_ENUMERATION(
       "SafeBrowsing.ReferrerAttributionResult.DownloadAttribution", result,
       SafeBrowsingNavigationObserverManager::ATTRIBUTION_FAILURE_TYPE_MAX);
   for (auto entry : attribution_chain)
-    *out_request->add_referrer_chain() = std::move(entry);
+    out_request->add_referrer_chain()->Swap(&entry);
 }
 
 }  // namespace safe_browsing