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diff --git a/chrome/browser/download/download_request_manager.h b/chrome/browser/download/download_request_manager.h
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+// Copyright (c) 2006-2008 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_REQUEST_MANAGER_H_
+#define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_MANAGER_H_
+
+#include <map>
+#include <vector>
+
+#include "base/ref_counted.h"
+
+class MessageLoop;
+class NavigationController;
+class TabContents;
+
+// DownloadRequestManager is responsible for determining whether a download
+// should be allowed or not. It is designed to keep pages from downloading
+// multiple files without user interaction. DownloadRequestManager is invoked
+// from ResourceDispatcherHost any time a download begins
+// (CanDownloadOnIOThread). The request is processed on the UI thread, and the
+// request is notified (back on the IO thread) as to whether the download should
+// be allowed or denied.
+//
+// Invoking CanDownloadOnIOThread notifies the callback and may update the
+// download status. The following details the various states:
+// . Each NavigationController initially starts out allowing a download
+//   (ALLOW_ONE_DOWNLOAD).
+// . The first time CanDownloadOnIOThread is invoked the download is allowed and
+//   the state changes to PROMPT_BEFORE_DOWNLOAD.
+// . If the state is PROMPT_BEFORE_DOWNLOAD and the user clicks the mouse,
+//   presses enter, the space bar or navigates to another page the state is
+//   reset to ALLOW_ONE_DOWNLOAD.
+// . If a download is attempted and the state is PROMPT_BEFORE_DOWNLOAD the user
+//   is prompted as to whether the download is allowed or disallowed. The users
+//   choice stays until the user navigates to a different host. For example, if
+//   the user allowed the download, multiple downloads are allowed without any
+//   user intervention until the user navigates to a different host.
+
+class DownloadRequestManager :
+    public base::RefCountedThreadSafe<DownloadRequestManager> {
+ public:
+  class TabDownloadState;
+
+  // Download status for a particular page. See class description for details.
+  enum DownloadStatus {
+    ALLOW_ONE_DOWNLOAD,
+    PROMPT_BEFORE_DOWNLOAD,
+    ALLOW_ALL_DOWNLOADS,
+    DOWNLOADS_NOT_ALLOWED
+  };
+
+  DownloadRequestManager(MessageLoop* io_loop, MessageLoop* ui_loop);
+  ~DownloadRequestManager();
+
+  // The callback from CanDownloadOnIOThread. This is invoked on the io thread.
+  class Callback {
+   public:
+    virtual void ContinueDownload() = 0;
+    virtual void CancelDownload() = 0;
+  };
+
+  // Returns the download status for a page. This does not change the state in
+  // anyway.
+  DownloadStatus GetDownloadStatus(TabContents* tab);
+
+  // Updates the state of the page as necessary and notifies the callback.
+  // WARNING: both this call and the callback are invoked on the io thread.
+  //
+  // DownloadRequestManager does not retain/release the Callback. It is up to
+  // the caller to ensure the callback is valid until the request is complete.
+  void CanDownloadOnIOThread(int render_process_host_id,
+                             int render_view_id,
+                             Callback* callback);
+
+  // Invoked when the user presses the mouse, enter key or space bar. This may
+  // change the download status for the page. See the class description for
+  // details.
+  void OnUserGesture(TabContents* tab);
+
+ private:
+  friend class DownloadRequestManagerTest;
+  friend class TabDownloadState;
+
+  // For unit tests. If non-null this is used instead of creating a dialog.
+  class TestingDelegate {
+   public:
+    virtual bool ShouldAllowDownload() = 0;
+  };
+  static void SetTestingDelegate(TestingDelegate* delegate);
+
+  // Gets the download state for the specified controller. If the
+  // TabDownloadState does not exist and |create| is true, one is created.
+  // See TabDownloadState's constructor description for details on the two
+  // controllers.
+  //
+  // The returned TabDownloadState is owned by the DownloadRequestManager and
+  // deleted when no longer needed (the Remove method is invoked).
+  TabDownloadState* GetDownloadState(
+      NavigationController* controller,
+      NavigationController* originating_controller,
+      bool create);
+
+  // CanDownloadOnIOThread invokes this on the UI thread. This determines the
+  // tab and invokes CanDownloadImpl.
+  void CanDownload(int render_process_host_id,
+                   int render_view_id,
+                   Callback* callback);
+
+  // Does the work of updating the download status on the UI thread and
+  // potentially prompting the user.
+  void CanDownloadImpl(TabContents* originating_tab,
+                       Callback* callback);
+
+  // Invoked on the UI thread. Schedules a call to NotifyCallback on the io
+  // thread.
+  void ScheduleNotification(Callback* callback, bool allow);
+
+  // Notifies the callback. This *must* be invoked on the IO thread.
+  void NotifyCallback(Callback* callback, bool allow);
+
+  // Removes the specified TabDownloadState from the internal map and deletes
+  // it. This has the effect of resetting the status for the tab to
+  // ALLOW_ONE_DOWNLOAD.
+  void Remove(TabDownloadState* state);
+
+  // Two threads we use. NULL during testing, in which case messages are
+  // dispatched immediately.
+  MessageLoop* io_loop_;
+  MessageLoop* ui_loop_;
+
+  // Maps from tab to download state. The download state for a tab only exists
+  // if the state is other than ALLOW_ONE_DOWNLOAD. Similarly once the state
+  // transitions from anything but ALLOW_ONE_DOWNLOAD back to ALLOW_ONE_DOWNLOAD
+  // the TabDownloadState is removed and deleted (by way of Remove).
+  typedef std::map<NavigationController*, TabDownloadState*> StateMap;
+  StateMap state_map_;
+
+  static TestingDelegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(DownloadRequestManager);
+};
+
+#endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_MANAGER_H_