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

content/public/browser/download_save_info.cc

Index: content/public/browser/download_save_info.cc
diff --git a/content/public/browser/download_save_info.cc b/content/public/browser/download_save_info.cc
index 3093ee6844570c5f6a82a056391272b61ccd1aaa..e4208411cc6c41a80841a5b51b44138f645f67d1 100644
--- a/content/public/browser/download_save_info.cc
+++ b/content/public/browser/download_save_info.cc
@@ -13,4 +13,13 @@ DownloadSaveInfo::DownloadSaveInfo()
 DownloadSaveInfo::~DownloadSaveInfo() {
 }
 
+DownloadSaveInfo::DownloadSaveInfo(DownloadSaveInfo&& that)
+    : file_path(std::move(that.file_path)),
+      suggested_name(std::move(that.suggested_name)),
+      file(std::move(that.file)),
+      offset(that.offset),
+      hash_state(std::move(that.hash_state)),
+      prefix_hash(std::move(that.prefix_hash)),
+      prompt_for_save_location(that.prompt_for_save_location) {}
+
 }  // namespace content