Mask the close button on the download shelf so that it's visible even in dark...

chrome/browser/views/download_shelf_view.h

Index: chrome/browser/views/download_shelf_view.h
===================================================================
--- chrome/browser/views/download_shelf_view.h	(revision 22523)
+++ chrome/browser/views/download_shelf_view.h	(working copy)
@@ -81,6 +81,12 @@
   // Returns true if the shelf is wide enough to show the first download item.
   bool CanFitFirstDownloadItem();
 
+  // Called on theme change.
+  void UpdateButtonColors();
+
+  // Overridden from views::View.
+  virtual void ThemeChanged();
+
   // The browser for this shelf.
   Browser* browser_;