DownloadManagerDelegate::ShouldCompleteDownload(callback)

chrome/browser/download/download_completion_blocker.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.
+
+#ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_COMPLETION_BLOCKER_H_
+#define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_COMPLETION_BLOCKER_H_
+#pragma once
+
+#include "base/callback.h"
+#include "content/public/browser/download_item.h"
+
+// A subsystem may use a DownloadCompletionBlocker in conjunction with
+// DownloadManagerDelegate::ShouldCompleteDownload() in order to block the
+// completion of a DownloadItem.

[Randy Smith (Not in Mondays), 2012/05/16 19:04:53]

I'd be explicit about the semantics of this class, i.e. that completion will
call the most recent specified callback, and will only call it once.  You might
also want to specify whether or not it's valid to call CompleteDownload()
multiple times (no, I don't have a use case, but to me that just means forbid it
:-}) and what happens if you do.

[benjhayden, 2012/05/16 19:42:30]

Done.

+class DownloadCompletionBlocker : public content::DownloadItem::ExternalData {
+ public:
+  DownloadCompletionBlocker();
+  virtual ~DownloadCompletionBlocker();
+
+  bool is_complete() const { return is_complete_; }
+
+  void set_callback(const base::Closure& callback) {
+    if (!is_complete())
+      callback_ = callback;
+  }
+
+  // Mark this download item as complete with respect to this blocker. Other
+  // blockers may continue to block the item. Run |callback_|.
+  // Subclasses must chain if they override this method.

[Randy Smith (Not in Mondays), 2012/05/16 19:04:53]

nit, suggestion: My guess as to what you meant by "chain" is "call this method
from their override", but I'm not sure; maybe be more explicit?

[benjhayden, 2012/05/16 19:42:30]

Done.

+  virtual void CompleteDownload();
+
+ private:
+  bool is_complete_;
+  base::Closure callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(DownloadCompletionBlocker);
+};
+
+#endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_COMPLETION_BLOCKER_H_