[Mac] Re-layout download shelf when danger state of item changes.

chrome/browser/ui/cocoa/download/download_item_controller.h

Index: chrome/browser/ui/cocoa/download/download_item_controller.h
diff --git a/chrome/browser/ui/cocoa/download/download_item_controller.h b/chrome/browser/ui/cocoa/download/download_item_controller.h
index e9373f3e583cd6aa3cb5beac9dcf5a980bc192a8..98bc960cfed40c5674430b04c14a8497cbf8ce64 100644
--- a/chrome/browser/ui/cocoa/download/download_item_controller.h
+++ b/chrome/browser/ui/cocoa/download/download_item_controller.h
@@ -34,7 +34,42 @@ class MenuModel;
 }
 
 // A controller class that manages one download item.
-
+//
+// The view hierarchy is as follows:
+//
+// DownloadItemController
+//  |
+//  |  A container that is showing one of its child views (progressView_ or
+//  |  dangerousDownloadView_) depending on whether the download is safe or not.
+//  |
+//  +-- progressView_ (instance of DownloadItemButton)
+//  |   |
+//  |   +-- cell_ (instance of DownloadItemCell)
+//  |
+//  +-- dangerousDownloadView_
+//      |
+//      |  Contains the dangerous download warning. Dependong on whether the
+//      |  download is dangerous (e.g. dangerous due to type of file), or
+//      |  malicious (e.g. downloaded from a known malware site) only one of
+//      |  dangerousButtonTweaker_ or maliciousButtonTweaker_ will be visible at
+//      |  one time.
+//      |
+//      +-- dangerousDownloadLabel_
+//      |
+//      +-- image_
+//      |
+//      +-- dangerousButtonTweaker_
+//      |
+//      |  Contains the 'Discard'/'Save' buttons for a dangerous download. This
+//      |  is a GTMWidthBasedTweaker that adjusts the width based on the text of
+//      |  buttons.
+//      |
+//      +-- maliciousButtonTweaker_
+//
+//         Contains the 'Discard' button and the drop down context menu button.
+//         This is a GTMWidthBasedTweaker that adjusts the width based on the
+//         text of the 'Discard' button.
+//
 @interface DownloadItemController : NSViewController {
  @private
   IBOutlet DownloadItemButton* progressView_;