[Downloads] Introduce GUIDs for downloads.

components/history/core/browser/download_database.h

 // 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.
 
 #ifndef COMPONENTS_HISTORY_CORE_BROWSER_DOWNLOAD_DATABASE_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_DOWNLOAD_DATABASE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 61 matching lines @@
   bool MigrateReferrer();
 
   // Returns true if able to successfully add the by_ext_id and by_ext_name
   // columns to the downloads table.
   bool MigrateDownloadedByExtension();
 
   // Returns true if able to successfully add the etag and last-modified columns
   // to the downloads table.
   bool MigrateDownloadValidators();
 
+  // Returns true if able to add GUID, hash and HTTP method columns to the
+  // download table.
+  bool MigrateHashHttpMethodAndGenerateGuids();
+
   // Creates the downloads table if needed.
   bool InitDownloadTable();
 
   // Used to quickly clear the downloads. First you would drop it, then you
   // would re-initialize it.
   bool DropDownloadTable();
 
  private:
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendDBTest,
                            ConfirmDownloadInProgressCleanup);
@@ skipping 24 matching lines @@
   // to use for respectively an undefined value and in case of a crash.
   DownloadInterruptReason download_interrupt_reason_none_;
   DownloadInterruptReason download_interrupt_reason_crash_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadDatabase);
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_DOWNLOAD_DATABASE_H_