Download shelf autohides on showing in shell, just same as regular open

chrome/browser/platform_util_mac.mm

 // 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.
 
 #include "chrome/browser/platform_util.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/mac/mac_logging.h"
 #import "base/mac/sdk_forward_declarations.h"
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/platform_util_internal.h"
 #include "content/public/browser/browser_thread.h"
 #include "url/gurl.h"
 
 namespace platform_util {
 
-void ShowItemInFolder(Profile* profile, const base::FilePath& full_path) {
+namespace internal {
+
+void PlatformShowItemInFolder(Profile* profile,
+                              const base::FilePath& full_path) {
   DCHECK([NSThread isMainThread]);
   NSString* path_string = base::SysUTF8ToNSString(full_path.value());
   if (!path_string || ![[NSWorkspace sharedWorkspace] selectFile:path_string
                                         inFileViewerRootedAtPath:@""])
     LOG(WARNING) << "NSWorkspace failed to select file " << full_path.value();
 }
 
+} // namespace internal
+
 void OpenFileOnMainThread(const base::FilePath& full_path) {
   DCHECK([NSThread isMainThread]);
   NSString* path_string = base::SysUTF8ToNSString(full_path.value());
   if (!path_string)
     return;
 
   // On Mavericks or later, NSWorkspaceLaunchWithErrorPresentation will
   // properly handle Finder activation for quarantined files
   // (http://crbug.com/32921) and unassociated file types
   // (http://crbug.com/50263).
@@ skipping 70 matching lines @@
           [[view window] isVisible]);
 }
 
 bool IsSwipeTrackingFromScrollEventsEnabled() {
   SEL selector = @selector(isSwipeTrackingFromScrollEventsEnabled);
   return [NSEvent respondsToSelector:selector]
       && [NSEvent performSelector:selector];
 }
 
 }  // namespace platform_util