[Downloads] Allow acquiring dangerous download file.

content/public/browser/download_item.h

Index: content/public/browser/download_item.h
diff --git a/content/public/browser/download_item.h b/content/public/browser/download_item.h
index e3e4d22e9410f74252978b45e15f60671fe259d2..4a9b469cdb19b890a3f8c870d7151e4b218c26ec 100644
--- a/content/public/browser/download_item.h
+++ b/content/public/browser/download_item.h
@@ -21,6 +21,7 @@
 #include <string>
 #include <vector>
 
+#include "base/callback_forward.h"
 #include "base/files/file_path.h"
 #include "base/string16.h"
 #include "base/supports_user_data.h"
@@ -81,6 +82,9 @@ class CONTENT_EXPORT DownloadItem : public base::SupportsUserData {
                                   // TARGET_DISPOSITION_OVERWRITE.
   };
 
+  // Callback used with AcquireFileAndDeleteDownload().
+  typedef base::Callback<void(const base::FilePath&)> AcquireFileCallback;
+
   static const char kEmptyFileHash[];
 
   // Interface that observers of a particular download must implement in order
@@ -140,6 +144,13 @@ class CONTENT_EXPORT DownloadItem : public base::SupportsUserData {
   // history.
   virtual void Delete(DeleteReason reason) = 0;
 
+  // Acquires the download file and deletes the download. Equivalent to calling
+  // |Delete(DELETE_DUE_TO_USER_DISCARD)| with the exception that the download
+  // file isn't deleted. The path to the file is passed to the |callback|. If
+  // the downloaded file is not available, then returned path will be empty.
+  virtual void AcquireFileAndDeleteDownload(

[benjhayden, 2013/05/14 20:48:05]

Method names containing "And" generally signal to me that the interface might be
cleaner if they were split up. In this case, why not let the caller call
AcquireFile() then Delete()?
In order to enforce the invariant !!download_file_ <=> IsInProgress(),
AcquireFile might call Cancel() or require callers to ensure that the item is
not in progress and DCHECK(!IsInProgress()).

[asanka, 2013/05/14 21:14:34]

The intention is for this operation to be atomic. This method would be called on
an IN_PROGRESS dangerous download to discard the DownloadItem but not the
download file.

Although, 'AcquireFileAndRemove' is probably a better name.

+      const AcquireFileCallback& callback) = 0;
+
   // Removes the download from the views and history.
   virtual void Remove() = 0;