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

content/public/browser/download_item.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.
 //
 // Each download is represented by a DownloadItem, and all DownloadItems
 // are owned by the DownloadManager which maintains a global list of all
 // downloads. DownloadItems are created when a user initiates a download,
 // and exist for the duration of the browser life time.
 //
 // Download observers:
@@ skipping 64 matching lines @@
     TARGET_DISPOSITION_PROMPT     // Prompt the user for the actual
                                   // target. Implies
                                   // TARGET_DISPOSITION_OVERWRITE.
   };
 
   // Callback used with AcquireFileAndDeleteDownload().
   typedef base::Callback<void(const base::FilePath&)> AcquireFileCallback;
 
   static const uint32_t kInvalidId;
 
-  static const char kEmptyFileHash[];
-
   // Interface that observers of a particular download must implement in order
   // to receive updates to the download's status.
   class CONTENT_EXPORT Observer {
    public:
     virtual void OnDownloadUpdated(DownloadItem* download) {}
     virtual void OnDownloadOpened(DownloadItem* download) {}
     virtual void OnDownloadRemoved(DownloadItem* download) {}
 
     // Called when the download is being destroyed. This happens after
     // every OnDownloadRemoved() as well as when the DownloadManager is going
@@ skipping 124 matching lines @@
   // return the path requested.
   virtual const base::FilePath& GetForcedFilePath() const = 0;
 
   // Returns the file-name that should be reported to the user. If a display
   // name has been explicitly set using SetDisplayName(), this function returns
   // that display name. Otherwise returns the final target filename.
   virtual base::FilePath GetFileNameToReportUser() const = 0;
 
   virtual TargetDisposition GetTargetDisposition() const = 0;
 
-  // Final hash of completely downloaded file; not valid if
-  // GetState() != COMPLETED.
+  // Final hash of completely downloaded file, or partial hash of an interrupted
+  // download; only valid if GetState() == COMPLETED or INTERRUPTED.
   virtual const std::string& GetHash() const = 0;
 
-  // Intermediate hash state, for persisting partial downloads.
-  virtual const std::string& GetHashState() const = 0;
-
   // True if the file associated with the download has been removed by
   // external action.
   virtual bool GetFileExternallyRemoved() const = 0;
 
   // If the file is successfully deleted, then GetFileExternallyRemoved() will
   // become true, GetFullPath() will become empty, and
   // DownloadItem::OnDownloadUpdated() will be called. Does nothing if
   // GetState() == COMPLETE or GetFileExternallyRemoved() is already true or
   // GetFullPath() is already empty. The callback is always run, and it is
   // always run asynchronously. It will be passed true if the file is
@@ skipping 83 matching lines @@
   // return |name|. Has no effect on the final target filename.
   virtual void SetDisplayName(const base::FilePath& name) = 0;
 
   // Debug/testing -------------------------------------------------------------
   virtual std::string DebugString(bool verbose) const = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_DOWNLOAD_ITEM_H_