Added AddDownload communication path and observers

content/public/browser/background_fetch_client.h

Index: content/public/browser/background_fetch_client.h
diff --git a/content/public/browser/background_fetch_client.h b/content/public/browser/background_fetch_client.h
index 1aad804e99a75da39665dfa15c39279bbc84c773..cfbadc57a0fc62fc7682b14c4ee9970118d82625 100644
--- a/content/public/browser/background_fetch_client.h
+++ b/content/public/browser/background_fetch_client.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "content/common/content_export.h"
+#include "url/gurl.h"
 
 namespace content {
 
@@ -40,6 +41,13 @@ class CONTENT_EXPORT BackgroundFetchClient {
   // reset the delegate back to a `nullptr` when it's being destructed.
   virtual void SetDelegate(Delegate* delegate) = 0;
 
+  // Notify the client that a Background Fetch download has started, including
+  // all information needed to display a notification of the download.
+  virtual void AddDownload(const GURL& url,
+                           const std::string& registration_id,
+                           const std::string& title,
+                           int64_t total_download_size) = 0;
+
  protected:
   virtual ~BackgroundFetchClient() {}
 };