[Downloads] Rework how hashes are calculated for download files.

content/public/test/mock_download_manager.cc

Index: content/public/test/mock_download_manager.cc
diff --git a/content/public/test/mock_download_manager.cc b/content/public/test/mock_download_manager.cc
index 07fbea86ac680128163240c1fa1cdb718a68a987..073e0864e95a2350928f521da638a034199d5075 100644
--- a/content/public/test/mock_download_manager.cc
+++ b/content/public/test/mock_download_manager.cc
@@ -24,6 +24,7 @@ MockDownloadManager::CreateDownloadItemAdapter::CreateDownloadItemAdapter(
     const std::string& last_modified,
     int64_t received_bytes,
     int64_t total_bytes,
+    const std::string& hash,
     DownloadItem::DownloadState state,
     DownloadDangerType danger_type,
     DownloadInterruptReason interrupt_reason,
@@ -40,6 +41,7 @@ MockDownloadManager::CreateDownloadItemAdapter::CreateDownloadItemAdapter(
       end_time(end_time),
       received_bytes(received_bytes),
       total_bytes(total_bytes),
+      hash(hash),
       state(state),
       danger_type(danger_type),
       interrupt_reason(interrupt_reason),
@@ -106,6 +108,7 @@ DownloadItem* MockDownloadManager::CreateDownloadItem(
     const std::string& last_modified,
     int64_t received_bytes,
     int64_t total_bytes,
+    const std::string& hash,
     DownloadItem::DownloadState state,
     DownloadDangerType danger_type,
     DownloadInterruptReason interrupt_reason,
@@ -124,6 +127,7 @@ DownloadItem* MockDownloadManager::CreateDownloadItem(
                                     last_modified,
                                     received_bytes,
                                     total_bytes,
+                                    hash,
                                     state,
                                     danger_type,
                                     interrupt_reason,