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

content/public/test/mock_download_manager.h

Index: content/public/test/mock_download_manager.h
diff --git a/content/public/test/mock_download_manager.h b/content/public/test/mock_download_manager.h
index 77a883f9a7beb9451379b810f8a0c3f628a305e1..cbed2cd7a9f7066928d870af2b603ed512230c7d 100644
--- a/content/public/test/mock_download_manager.h
+++ b/content/public/test/mock_download_manager.h
@@ -43,6 +43,7 @@ class MockDownloadManager : public DownloadManager {
     std::string last_modified;
     int64_t received_bytes;
     int64_t total_bytes;
+    std::string hash;
     DownloadItem::DownloadState state;
     DownloadDangerType danger_type;
     DownloadInterruptReason interrupt_reason;
@@ -61,6 +62,7 @@ class MockDownloadManager : public DownloadManager {
                               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,
@@ -116,6 +118,7 @@ class MockDownloadManager : public DownloadManager {
                                    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,