Add download item tooltips on linux/win.

chrome/browser/gtk/download_item_gtk.h

 // Copyright (c) 2009 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_GTK_DOWNLOAD_ITEM_GTK_H_
 #define CHROME_BROWSER_GTK_DOWNLOAD_ITEM_GTK_H_
 
 #include <gtk/gtk.h>
 
 #include <string>
@@ skipping 58 matching lines @@
 
   // Starts a repeating timer for UpdateDownloadProgress.
   void StartDownloadProgress();
 
   // Stops the repeating timer.
   void StopDownloadProgress();
 
   // Ask the icon manager to asynchronously start loading the icon for the file.
   void LoadIcon();
 
+  // Sets the tooltip on the download button.
+  void UpdateTooltip();
+
   // Sets the name label to the correct color.
   void UpdateNameLabel();
 
   // Sets the text with the correct color if |status_label| exists.
   void UpdateStatusLabel(GtkWidget* status_label,
                          const std::string& status_text);
 
   // Sets the components of the danger warning.
   void UpdateDangerWarning();
 
@@ skipping 115 matching lines @@
   NotificationRegistrar registrar_;
 
   // The time at which we were insantiated.
   base::Time creation_time_;
 
   // For canceling an in progress icon request.
   CancelableRequestConsumerT<int, 0> icon_consumer_;
 };
 
 #endif  // CHROME_BROWSER_GTK_DOWNLOAD_ITEM_GTK_H_