[downloads] Correctly plumb client ID for download file scanning.

content/browser/download/download_manager_impl.cc

Index: content/browser/download/download_manager_impl.cc
diff --git a/content/browser/download/download_manager_impl.cc b/content/browser/download/download_manager_impl.cc
index ec6eabc73ea89d88bc9d8efacc12a172847ccd88..92f81fe7f92050c3d737da978394ff140131f5a6 100644
--- a/content/browser/download/download_manager_impl.cc
+++ b/content/browser/download/download_manager_impl.cc
@@ -415,6 +415,12 @@ void DownloadManagerImpl::OnFileExistenceChecked(uint32_t download_id,
   }
 }
 
+std::string DownloadManagerImpl::GetApplicationClientIdForFileScanning() const {
+  if (delegate_)
+    return delegate_->ApplicationClientIdForFileScanning();
+  return std::string();
+}
+
 BrowserContext* DownloadManagerImpl::GetBrowserContext() const {
   return browser_context_;
 }