Adding status info to DownloadUIItem and piping it through.

components/offline_pages/core/downloads/download_ui_item.h

 // Copyright 2016 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.
 
 #ifndef COMPONENTS_OFFLINE_PAGES_CORE_DOWNLOADS_DOWNLOAD_UI_ITEM_H_
 #define COMPONENTS_OFFLINE_PAGES_CORE_DOWNLOADS_DOWNLOAD_UI_ITEM_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/time/time.h"
 #include "url/gurl.h"
 
 namespace offline_pages {
 
 struct OfflinePageItem;
 class SavePageRequest;
 
+// The abstract "download item" that may be a media file, a web page (together
+// with all the resources) or a PWA web package. This is a data bag that exposes
+// only bits potentially visible by the user, not the internal data.
 struct DownloadUIItem {
  public:
+  // All Items start from PENDING and terminate at COMPLETED or are removed.
+  // In sync with state values in Java OfflinePageDownloadItem class.
+  enum DownloadState {
+    PENDING = 0,
+    DOWNLOADING = 1,
+    PAUSED = 2,
+    COMPLETED = 3,
+  };
+
+  // The abstract notion of download progress. The |current| is always less
+  // than |max|, the download 'percentage' at any moment is current/max.
+  // Note the |max| can change over time, as more resources are discovered from
+  // the bytes already loaded (which is often happening when a web page is
+  // loaded and more resources are found in the markup).
+  struct DownloadProgress {
+    DownloadProgress(int64_t current, int64_t max)
+      : current(current),
+        max(max) {}
+
+    int64_t current;
+    int64_t max;
+  };
+
   DownloadUIItem();
   explicit DownloadUIItem(const OfflinePageItem& page);
   explicit DownloadUIItem(const SavePageRequest& request);
   DownloadUIItem(const DownloadUIItem& other);
   ~DownloadUIItem();
 
-  // Unique id.
+  // Unique id. Not necesarily a GUID, may be any string unique in the Chrome
+  // instance across all DownloadUIItem providers.
   std::string guid;
 
   // The URL of the captured page.
   GURL url;
 
+  DownloadState download_state;
+
+  DownloadProgress download_progress;
+
   // The Title of the captured page, if any. It can be empty string either
   // because the page is not yet fully loaded, or because it doesn't have any.
   base::string16 title;
 
   // The file path to the archive with a local copy of the page.
   base::FilePath target_path;
 
   // The time when the offline archive was created.
   base::Time start_time;
 
   // The size of the offline copy.
   int64_t total_bytes;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_CORE_DOWNLOADS_DOWNLOAD_UI_ITEM_H_